diff --git a/docs/UserGuide.md b/docs/UserGuide.md
index 39c83cb4..57a4d56d 100644
--- a/docs/UserGuide.md
+++ b/docs/UserGuide.md
@@ -165,15 +165,30 @@ If metadata has been extracted by GPT, this section displays structured informat
 - Understanding the complete data structure
 
 #### Document Previews
-View your documents side-by-side in embedded PDF viewers:
+View your documents with type-specific viewers:
 - **Original Document**: The immutable original file as first ingested, before any processing
 - **Processed Document**: The final file with embedded metadata
 
-**Features**:
-- In-browser PDF rendering for immediate viewing
-- Side-by-side comparison of original vs processed versions
-- Full 600px height previews for detailed review
-- **View Extracted Text** buttons below each preview to see the full text content
+**PDF Preview (pdf.js)**:
+- In-browser PDF rendering via pdf.js — no native browser PDF plugin required
+- Page navigation controls (previous / next) with page counter
+- High-quality canvas-based rendering that works consistently across browsers
+- Side-by-side comparison of original vs processed versions on the detail page
+
+**Image Preview (JPEG, PNG, TIFF, WebP)**:
+- In-browser image display with zoom and pan controls
+- Zoom in / out buttons and mouse-wheel zoom
+- Click-and-drag panning for large or zoomed images
+- Reset button to return to the original size
+- Zoom percentage indicator
+
+**Text File Preview**:
+- Syntax-highlighted display with line numbers
+- Monospace font for readable code and data
+- Copy-to-clipboard button for the full text content
+- Supports plain text, CSV, source code, and other text MIME types
+
+**View Extracted Text** buttons below each preview to see the full text content
 
 **Text Extraction Modals**: Click "View Extracted Text" to open a fullscreen modal showing:
 - Complete extracted text from OCR or PDF text layer
@@ -218,10 +233,18 @@ If your file is still available on disk, you can preview it directly in the brow
 - **Processed File**: The file after metadata has been embedded (if processing completed)
 
 Both previews support:
-- In-browser PDF viewing with embedded viewer
+- In-browser PDF viewing with pdf.js (canvas-based, no browser plugin needed)
+- Image viewing with zoom/pan for JPEG, PNG, TIFF, and WebP
+- Text file viewing with line numbers for plain text, CSV, and source code
 - Side-by-side comparison of original and processed versions
 - Full text extraction viewing via modal overlays
 
+**Quick Preview from File List**: On the main Files page, each file row includes an eye icon button that opens a slide-out side panel with a quick preview. This lets you:
+- Preview PDFs, images, and text files without leaving the file list
+- Navigate PDF pages within the panel
+- Zoom and pan images
+- Open the full document view or download the file from the panel footer
+
 **View Extracted Text**: Each preview includes a button to view the complete extracted text in a fullscreen modal. When you click this button:
 - The system extracts text from the PDF file on-demand using pypdf
 - A loading indicator shows while extraction is in progress
diff --git a/frontend/templates/file_detail.html b/frontend/templates/file_detail.html
index f329b6c2..48029c20 100644
--- a/frontend/templates/file_detail.html
+++ b/frontend/templates/file_detail.html
@@ -1528,11 +1528,11 @@
   {% endif %}
 
   <!-- File Preview Card -->
-  {% if file_exists or processed_exists %}
+  {% if original_file_exists or processed_file_exists %}
   <div class="detail-card">
     <h3>File Previews</h3>
     <div style="display: grid; grid-template-columns: repeat(auto-fit, minmax(400px, 1fr)); gap: 2rem;">
-      {% if file_exists %}
+      {% if original_file_exists %}
       <div>
         <h4 style="font-weight: 600; color: #2d3748; margin-bottom: 1rem;">Original File</h4>
         <div style="border: 2px solid #e2e8f0; border-radius: 0.5rem; overflow: hidden; background-color: #f7fafc;">
@@ -1541,36 +1541,46 @@
           <img src="/api/files/{{ file.id }}/preview?version=original" alt="{{ file.original_filename }}" style="width: 100%; height: auto; display: block;">
           {% elif file.mime_type and file.mime_type.startswith('text/') %}
           <!-- Text file preview -->
-          <iframe src="/api/files/{{ file.id }}/preview?version=original" style="width: 100%; height: 600px; border: none;"></iframe>
+          <iframe src="/api/files/{{ file.id }}/preview?version=original" title="Original text file preview" style="width: 100%; height: 600px; border: none;"></iframe>
           {% else %}
-          <!-- PDF and other documents -->
-          <iframe src="/api/files/{{ file.id }}/preview?version=original" style="width: 100%; height: 600px; border: none;"></iframe>
+          <!-- PDF via pdf.js (rendered by loadPDF above) — fallback canvas container -->
+          <div id="detail-original-canvas" class="pdf-canvas-wrapper" style="min-height: 400px; display: flex; justify-content: center; align-items: center; padding: 0.5rem;">
+            <div class="pdf-loading">
+              <i class="fas fa-file-pdf" aria-hidden="true" style="font-size: 2rem; margin-bottom: 1rem; color: #94a3b8;"></i>
+              <p>This PDF is displayed in the Document Previews section at the top of the page.</p>
+            </div>
+          </div>
           {% endif %}
         </div>
         <div style="margin-top: 0.5rem; text-align: center; display: flex; gap: 1rem; justify-content: center;">
           <a href="/api/files/{{ file.id }}/preview?version=original" target="_blank" style="color: #3182ce; text-decoration: none; font-size: 0.875rem;">
-            <i class="fas fa-external-link-alt"></i> Open in new tab
+            <i class="fas fa-external-link-alt" aria-hidden="true"></i> Open in new tab
           </a>
           <a href="/api/files/{{ file.id }}/download?version=original" style="color: #3182ce; text-decoration: none; font-size: 0.875rem;">
-            <i class="fas fa-download"></i> Download
+            <i class="fas fa-download" aria-hidden="true"></i> Download
           </a>
         </div>
       </div>
       {% endif %}
 
-      {% if processed_exists %}
+      {% if processed_file_exists %}
       <div>
         <h4 style="font-weight: 600; color: #2d3748; margin-bottom: 1rem;">Processed File</h4>
         <div style="border: 2px solid #e2e8f0; border-radius: 0.5rem; overflow: hidden; background-color: #f7fafc;">
-          <!-- Processed files are typically PDFs -->
-          <iframe src="/api/files/{{ file.id }}/preview?version=processed" style="width: 100%; height: 600px; border: none;"></iframe>
+          <!-- Processed files are typically PDFs — rendered by pdf.js above -->
+          <div style="min-height: 400px; display: flex; justify-content: center; align-items: center; padding: 0.5rem;">
+            <div class="pdf-loading">
+              <i class="fas fa-file-pdf" aria-hidden="true" style="font-size: 2rem; margin-bottom: 1rem; color: #94a3b8;"></i>
+              <p>This PDF is displayed in the Document Previews section at the top of the page.</p>
+            </div>
+          </div>
         </div>
         <div style="margin-top: 0.5rem; text-align: center; display: flex; gap: 1rem; justify-content: center;">
           <a href="/api/files/{{ file.id }}/preview?version=processed" target="_blank" style="color: #3182ce; text-decoration: none; font-size: 0.875rem;">
-            <i class="fas fa-external-link-alt"></i> Open in new tab
+            <i class="fas fa-external-link-alt" aria-hidden="true"></i> Open in new tab
           </a>
           <a href="/api/files/{{ file.id }}/download?version=processed" style="color: #3182ce; text-decoration: none; font-size: 0.875rem;">
-            <i class="fas fa-download"></i> Download
+            <i class="fas fa-download" aria-hidden="true"></i> Download
           </a>
         </div>
       </div>
diff --git a/frontend/templates/file_view.html b/frontend/templates/file_view.html
index 0aaa77fd..873ab6e7 100644
--- a/frontend/templates/file_view.html
+++ b/frontend/templates/file_view.html
@@ -3,6 +3,11 @@
 
 {% block head_extra %}
   <script src="/static/js/common.js"></script>
+  <!-- PDF.js library (Apache 2.0 License - compatible) -->
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js"></script>
+  <script>
+    pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js';
+  </script>
   <style>
     .doc-container { max-width: 1200px; margin: 0 auto; }
 
@@ -51,7 +56,61 @@
     /* ── tags ── */
     .tag-pill { display: inline-block; padding: 0.15rem 0.6rem; border-radius: 9999px; font-size: 0.75rem; font-weight: 500; background: #f0fdf4; color: #15803d; margin: 0.1rem; }
 
-    /* ── preview iframe ── */
+    /* ── pdf.js viewer ── */
+    .pdf-viewer { position: relative; background: #525659; border-radius: 0.375rem; overflow: hidden; }
+    .pdf-controls {
+      display: flex; align-items: center; justify-content: center; gap: 0.75rem;
+      padding: 0.5rem; background: #f1f5f9; border-radius: 0.375rem 0.375rem 0 0;
+    }
+    .pdf-nav-btn {
+      padding: 0.35rem 0.75rem; border: 1px solid #cbd5e1; border-radius: 0.25rem;
+      background: white; color: #374151; font-size: 0.8rem; cursor: pointer;
+      min-height: 36px; min-width: 36px;
+    }
+    .pdf-nav-btn:disabled { opacity: 0.4; cursor: default; }
+    .pdf-nav-btn:hover:not(:disabled) { background: #e2e8f0; }
+    .pdf-page-info { font-size: 0.8rem; color: #374151; font-weight: 600; min-width: 100px; text-align: center; }
+    .pdf-canvas-wrap { display: flex; justify-content: center; padding: 0.75rem; min-height: 400px; max-height: 700px; overflow: auto; }
+    .pdf-canvas-wrap canvas { max-width: 100%; height: auto; }
+
+    /* ── image viewer with zoom/pan ── */
+    .img-viewer { position: relative; background: #f1f5f9; border-radius: 0.375rem; overflow: hidden; }
+    .img-controls {
+      display: flex; align-items: center; justify-content: center; gap: 0.5rem;
+      padding: 0.5rem; background: #f1f5f9; border-radius: 0.375rem 0.375rem 0 0;
+    }
+    .img-controls button {
+      padding: 0.35rem 0.6rem; border: 1px solid #cbd5e1; border-radius: 0.25rem;
+      background: white; color: #374151; font-size: 0.85rem; cursor: pointer;
+      min-height: 36px; min-width: 36px;
+    }
+    .img-controls button:hover { background: #e2e8f0; }
+    .img-wrap {
+      display: flex; justify-content: center; align-items: center;
+      overflow: auto; max-height: 650px; min-height: 300px; cursor: grab;
+      padding: 0.5rem; background: #525659;
+    }
+    .img-wrap.dragging { cursor: grabbing; }
+    .img-wrap img { transition: transform 0.15s ease; transform-origin: center center; }
+
+    /* ── text viewer ── */
+    .text-viewer { border-radius: 0.375rem; overflow: hidden; }
+    .text-viewer-header {
+      display: flex; align-items: center; justify-content: space-between;
+      padding: 0.5rem 0.75rem; background: #f1f5f9; border-radius: 0.375rem 0.375rem 0 0;
+    }
+    .text-viewer-header span { font-size: 0.8rem; color: #374151; font-weight: 600; }
+    .text-content {
+      background: #1e293b; color: #e2e8f0; padding: 1rem; font-family: 'SFMono-Regular', Consolas, monospace;
+      font-size: 0.82rem; line-height: 1.65; max-height: 600px; overflow: auto; white-space: pre-wrap; word-break: break-word;
+      tab-size: 4;
+    }
+    .text-content .line-number {
+      display: inline-block; width: 3.5em; color: #64748b; text-align: right;
+      margin-right: 1em; user-select: none; font-size: 0.75rem;
+    }
+
+    /* ── preview iframe fallback ── */
     .preview-frame { width: 100%; height: 600px; border: none; border-radius: 0.375rem; background: #f1f5f9; display: block; }
 
     /* ── text box ── */
@@ -271,27 +330,75 @@
       </div>
     </div>
 
-    <!-- RIGHT: PDF preview -->
+    <!-- RIGHT: Document preview -->
     <div>
       <div class="doc-card" style="padding:1rem;">
+        {% set preview_mime = file.mime_type or 'application/pdf' %}
+        {% set preview_version = 'processed' if processed_file_exists else 'original' %}
+        {% set has_preview = processed_file_exists or original_file_exists %}
+
+        {% if preview_mime.startswith('image/') %}
+        <div class="doc-card-title"><i class="fas fa-image" aria-hidden="true" style="color:#8b5cf6;margin-right:0.4rem;"></i>Preview</div>
+        {% elif preview_mime.startswith('text/') %}
+        <div class="doc-card-title"><i class="fas fa-file-code" aria-hidden="true" style="color:#059669;margin-right:0.4rem;"></i>Preview</div>
+        {% else %}
         <div class="doc-card-title"><i class="fas fa-file-pdf" aria-hidden="true" style="color:#ef4444;margin-right:0.4rem;"></i>Preview</div>
-        {% if processed_file_exists %}
-          <iframe
-            src="/api/files/{{ file.id }}/preview?version=processed"
-            class="preview-frame"
-            title="Processed document preview">
-          </iframe>
-          <div style="font-size:0.75rem;color:#9ca3af;margin-top:0.4rem;text-align:right;">Processed version</div>
-        {% elif original_file_exists %}
-          <iframe
-            src="/api/files/{{ file.id }}/preview?version=original"
-            class="preview-frame"
-            title="Original document preview">
-          </iframe>
-          <div style="font-size:0.75rem;color:#9ca3af;margin-top:0.4rem;text-align:right;">Original version</div>
+        {% endif %}
+
+        {% if has_preview %}
+          {% if preview_mime.startswith('image/') %}
+          <!-- ── Image viewer with zoom / pan ── -->
+          <div class="img-viewer" id="img-viewer">
+            <div class="img-controls">
+              <button onclick="imgZoom(1.25)" title="Zoom in" aria-label="Zoom in"><i class="fas fa-search-plus" aria-hidden="true"></i></button>
+              <button onclick="imgZoom(0.8)" title="Zoom out" aria-label="Zoom out"><i class="fas fa-search-minus" aria-hidden="true"></i></button>
+              <button onclick="imgReset()" title="Reset zoom" aria-label="Reset zoom"><i class="fas fa-expand" aria-hidden="true"></i></button>
+              <span id="img-zoom-level" style="font-size:0.8rem;color:#6b7280;min-width:3em;text-align:center;">100%</span>
+            </div>
+            <div class="img-wrap" id="img-wrap">
+              <img
+                id="preview-img"
+                src="/api/files/{{ file.id }}/preview?version={{ preview_version }}"
+                alt="{{ file.original_filename }}"
+                draggable="false"
+                style="max-width:100%;height:auto;">
+            </div>
+          </div>
+
+          {% elif preview_mime.startswith('text/') %}
+          <!-- ── Text file viewer with line numbers ── -->
+          <div class="text-viewer" id="text-viewer">
+            <div class="text-viewer-header">
+              <span><i class="fas fa-file-code" aria-hidden="true" style="margin-right:0.3rem;"></i>{{ file.original_filename }}</span>
+              <button class="text-toggle" onclick="copyTextPreview()" id="text-copy-btn" aria-label="Copy file text">
+                <i class="fas fa-copy" aria-hidden="true"></i> Copy
+              </button>
+            </div>
+            <div class="text-content" id="text-preview-content" aria-live="polite">
+              <div style="text-align:center;padding:2rem;color:#94a3b8;"><i class="fas fa-spinner fa-spin" aria-hidden="true"></i> Loading…</div>
+            </div>
+          </div>
+
+          {% else %}
+          <!-- ── PDF viewer (pdf.js) ── -->
+          <div class="pdf-viewer" id="pdf-viewer">
+            <div class="pdf-controls">
+              <button class="pdf-nav-btn" onclick="pdfChangePage(-1)" id="pdf-prev-btn" aria-label="Previous page"><i class="fas fa-chevron-left" aria-hidden="true"></i></button>
+              <span class="pdf-page-info" id="pdf-page-info" aria-live="polite">Loading…</span>
+              <button class="pdf-nav-btn" onclick="pdfChangePage(1)" id="pdf-next-btn" aria-label="Next page"><i class="fas fa-chevron-right" aria-hidden="true"></i></button>
+            </div>
+            <div class="pdf-canvas-wrap" id="pdf-canvas-wrap">
+              <div style="text-align:center;padding:3rem;color:#94a3b8;">
+                <i class="fas fa-spinner fa-spin" aria-hidden="true" style="font-size:2rem;margin-bottom:0.75rem;"></i>
+                <p>Loading PDF…</p>
+              </div>
+            </div>
+          </div>
+          {% endif %}
+          <div style="font-size:0.75rem;color:#9ca3af;margin-top:0.4rem;text-align:right;">{{ 'Processed' if processed_file_exists else 'Original' }} version</div>
         {% else %}
           <div style="display:flex;flex-direction:column;align-items:center;justify-content:center;height:300px;background:#f9fafb;border-radius:0.375rem;color:#9ca3af;">
-            <i class="fas fa-file-pdf" style="font-size:3rem;margin-bottom:1rem;opacity:0.4;"></i>
+            <i class="fas fa-file" aria-hidden="true" style="font-size:3rem;margin-bottom:1rem;opacity:0.4;"></i>
             <p>No file available for preview</p>
           </div>
         {% endif %}
@@ -338,7 +445,7 @@
 </div>
 
 <script>
-  // Toggle inline OCR text visibility
+  // ── Toggle inline OCR text visibility ──
   function toggleOcrText() {
     var block = document.getElementById('ocr-text-block');
     var icon  = document.getElementById('ocr-toggle-icon');
@@ -357,7 +464,7 @@
     }
   }
 
-  // Copy OCR text to clipboard
+  // ── Copy OCR text to clipboard ──
   function copyOcrText() {
     var content = document.getElementById('ocr-text-content');
     if (!content) return;
@@ -369,8 +476,6 @@
       btn.innerHTML = '<i class="fas fa-check"></i> Copied!';
       setTimeout(function() { btn.innerHTML = orig; }, 2000);
     }).catch(function() {
-      // Legacy clipboard fallback for browsers without Secure Context / navigator.clipboard
-      // (pre-2018 environments, e.g. HTTP-only or older Safari). Retained for maximum compatibility.
       try {
         var ta = document.createElement('textarea');
         ta.value = text;
@@ -385,7 +490,7 @@
     });
   }
 
-  // On-demand text extraction (when ocr_text not in DB)
+  // ── On-demand text extraction (when ocr_text not in DB) ──
   var _textCache = null;
   function loadText(fileId) {
     var area = document.getElementById('text-load-area');
@@ -414,5 +519,168 @@
     pre.textContent = text;
     container.appendChild(pre);
   }
+
+  // ── PDF.js viewer ──
+  var _pdfState = { doc: null, page: 1, total: 0 };
+
+  function pdfInit(url) {
+    var wrap = document.getElementById('pdf-canvas-wrap');
+    if (!wrap) return;
+    pdfjsLib.getDocument(url).promise.then(function(pdf) {
+      _pdfState.doc = pdf;
+      _pdfState.total = pdf.numPages;
+      _pdfState.page = 1;
+      pdfRenderPage();
+    }).catch(function() {
+      wrap.innerHTML = '<div style="text-align:center;padding:2rem;color:#f87171;"><i class="fas fa-exclamation-triangle" style="font-size:2rem;margin-bottom:0.5rem;"></i><p>Failed to load PDF</p></div>';
+    });
+  }
+
+  function pdfRenderPage() {
+    var wrap = document.getElementById('pdf-canvas-wrap');
+    if (!_pdfState.doc || !wrap) return;
+    _pdfState.doc.getPage(_pdfState.page).then(function(page) {
+      var vp = page.getViewport({ scale: 1.0 });
+      var scale = Math.min(wrap.clientWidth / vp.width, 2.0);
+      var svp = page.getViewport({ scale: scale });
+      var canvas = document.createElement('canvas');
+      canvas.width = svp.width;
+      canvas.height = svp.height;
+      canvas.style.maxWidth = '100%';
+      canvas.style.height = 'auto';
+      wrap.innerHTML = '';
+      wrap.appendChild(canvas);
+      page.render({ canvasContext: canvas.getContext('2d'), viewport: svp });
+      pdfUpdateInfo();
+    });
+  }
+
+  function pdfChangePage(delta) {
+    var np = _pdfState.page + delta;
+    if (np >= 1 && np <= _pdfState.total) {
+      _pdfState.page = np;
+      pdfRenderPage();
+    }
+  }
+
+  function pdfUpdateInfo() {
+    var info = document.getElementById('pdf-page-info');
+    if (info) info.textContent = 'Page ' + _pdfState.page + ' of ' + _pdfState.total;
+    var prev = document.getElementById('pdf-prev-btn');
+    var next = document.getElementById('pdf-next-btn');
+    if (prev) prev.disabled = _pdfState.page <= 1;
+    if (next) next.disabled = _pdfState.page >= _pdfState.total;
+  }
+
+  // ── Image viewer with zoom / pan ──
+  var _imgScale = 1;
+
+  function imgZoom(factor) {
+    _imgScale = Math.max(0.25, Math.min(5, _imgScale * factor));
+    var img = document.getElementById('preview-img');
+    if (img) img.style.transform = 'scale(' + _imgScale + ')';
+    var label = document.getElementById('img-zoom-level');
+    if (label) label.textContent = Math.round(_imgScale * 100) + '%';
+  }
+
+  function imgReset() {
+    _imgScale = 1;
+    var img = document.getElementById('preview-img');
+    if (img) img.style.transform = 'scale(1)';
+    var label = document.getElementById('img-zoom-level');
+    if (label) label.textContent = '100%';
+  }
+
+  // Mouse-drag panning for image viewer
+  (function() {
+    var wrap = document.getElementById('img-wrap');
+    if (!wrap) return;
+    var dragging = false, startX, startY, scrollL, scrollT;
+    wrap.addEventListener('mousedown', function(e) {
+      dragging = true; wrap.classList.add('dragging');
+      startX = e.pageX - wrap.offsetLeft; startY = e.pageY - wrap.offsetTop;
+      scrollL = wrap.scrollLeft; scrollT = wrap.scrollTop;
+    });
+    wrap.addEventListener('mousemove', function(e) {
+      if (!dragging) return; e.preventDefault();
+      wrap.scrollLeft = scrollL - (e.pageX - wrap.offsetLeft - startX);
+      wrap.scrollTop  = scrollT - (e.pageY - wrap.offsetTop  - startY);
+    });
+    wrap.addEventListener('mouseup', function() { dragging = false; wrap.classList.remove('dragging'); });
+    wrap.addEventListener('mouseleave', function() { dragging = false; wrap.classList.remove('dragging'); });
+    // Mouse wheel zoom
+    wrap.addEventListener('wheel', function(e) {
+      e.preventDefault();
+      imgZoom(e.deltaY < 0 ? 1.1 : 0.9);
+    }, { passive: false });
+  })();
+
+  // ── Text file viewer ──
+  function loadTextPreview(url) {
+    var container = document.getElementById('text-preview-content');
+    if (!container) return;
+    fetch(url)
+      .then(function(r) { if (!r.ok) throw new Error('HTTP ' + r.status); return r.text(); })
+      .then(function(text) {
+        container.innerHTML = '';
+        var lines = text.split('\n');
+        for (var i = 0; i < lines.length; i++) {
+          var lineEl = document.createElement('div');
+          var numSpan = document.createElement('span');
+          numSpan.className = 'line-number';
+          numSpan.textContent = (i + 1) + '';
+          lineEl.appendChild(numSpan);
+          lineEl.appendChild(document.createTextNode(lines[i]));
+          container.appendChild(lineEl);
+        }
+      })
+      .catch(function() {
+        container.innerHTML = '<div style="color:#f87171;padding:1rem;">Failed to load file content</div>';
+      });
+  }
+
+  function copyTextPreview() {
+    var container = document.getElementById('text-preview-content');
+    if (!container) return;
+    var lines = container.querySelectorAll('div');
+    var text = [];
+    lines.forEach(function(line) {
+      var clone = line.cloneNode(true);
+      var num = clone.querySelector('.line-number');
+      if (num) num.remove();
+      text.push(clone.textContent);
+    });
+    var btn = document.getElementById('text-copy-btn');
+    var orig = btn.innerHTML;
+    navigator.clipboard.writeText(text.join('\n')).then(function() {
+      btn.innerHTML = '<i class="fas fa-check"></i> Copied!';
+      setTimeout(function() { btn.innerHTML = orig; }, 2000);
+    }).catch(function() {
+      try {
+        var ta = document.createElement('textarea');
+        ta.value = text.join('\n');
+        ta.style.cssText = 'position:fixed;opacity:0;';
+        document.body.appendChild(ta);
+        ta.select();
+        document.execCommand('copy');
+        document.body.removeChild(ta);
+        btn.innerHTML = '<i class="fas fa-check"></i> Copied!';
+        setTimeout(function() { btn.innerHTML = orig; }, 2000);
+      } catch(e) {}
+    });
+  }
+
+  // ── Initialise on load ──
+  document.addEventListener('DOMContentLoaded', function() {
+    {% if (processed_file_exists or original_file_exists) and file %}
+      {% set pv = 'processed' if processed_file_exists else 'original' %}
+      {% set pm = file.mime_type or 'application/pdf' %}
+      {% if pm.startswith('text/') %}
+        loadTextPreview('/api/files/{{ file.id }}/preview?version={{ pv }}');
+      {% elif not pm.startswith('image/') %}
+        pdfInit('/api/files/{{ file.id }}/preview?version={{ pv }}');
+      {% endif %}
+    {% endif %}
+  });
 </script>
 {% endblock %}
diff --git a/frontend/templates/files.html b/frontend/templates/files.html
index 8daee476..b9b57225 100644
--- a/frontend/templates/files.html
+++ b/frontend/templates/files.html
@@ -3,6 +3,11 @@
 
 {% block head_extra %}
   <script src="/static/js/common.js"></script>
+  <!-- PDF.js library for in-browser PDF preview -->
+  <script src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.min.js"></script>
+  <script>
+    pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js';
+  </script>
   <script>
     window.uploadConfig = {
       concurrency: {{ upload_concurrency }},
@@ -340,6 +345,80 @@
       border-radius: 0.25rem;
       margin-bottom: 1rem;
     }
+
+    /* ── Preview modal (side panel) ── */
+    .preview-overlay {
+      display: none; position: fixed; inset: 0; z-index: 1000;
+      background: rgba(0,0,0,0.5); justify-content: flex-end;
+    }
+    .preview-overlay.active { display: flex; }
+    .preview-panel {
+      width: 55%; max-width: 720px; min-width: 340px; height: 100%;
+      background: white; box-shadow: -4px 0 20px rgba(0,0,0,0.15);
+      display: flex; flex-direction: column; animation: slideIn 0.2s ease;
+    }
+    @keyframes slideIn { from { transform: translateX(100%); } to { transform: translateX(0); } }
+    @media (max-width: 768px) { .preview-panel { width: 100%; max-width: 100%; } }
+    .preview-panel-header {
+      display: flex; align-items: center; justify-content: space-between;
+      padding: 0.75rem 1rem; border-bottom: 1px solid #e5e7eb; flex-shrink: 0;
+    }
+    .preview-panel-header h3 { font-size: 1rem; font-weight: 600; color: #1f2937; margin: 0; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
+    .preview-panel-close {
+      background: none; border: none; cursor: pointer; padding: 0.5rem;
+      color: #6b7280; font-size: 1.25rem; min-height: 44px; min-width: 44px;
+      display: flex; align-items: center; justify-content: center;
+    }
+    .preview-panel-close:hover { color: #1f2937; }
+    .preview-panel-body { flex: 1; overflow: auto; padding: 0; background: #f9fafb; }
+    .preview-panel-footer {
+      display: flex; align-items: center; justify-content: center; gap: 0.75rem;
+      padding: 0.75rem 1rem; border-top: 1px solid #e5e7eb; flex-shrink: 0;
+    }
+    .preview-panel-footer a, .preview-panel-footer button {
+      display: inline-flex; align-items: center; gap: 0.3rem;
+      padding: 0.4rem 0.9rem; border-radius: 0.25rem; font-size: 0.85rem; font-weight: 600;
+      text-decoration: none; cursor: pointer; border: 1px solid #d1d5db; background: white; color: #374151;
+      min-height: 40px;
+    }
+    .preview-panel-footer a:hover, .preview-panel-footer button:hover { background: #f3f4f6; }
+    /* PDF controls inside preview modal */
+    .pm-pdf-controls {
+      display: flex; align-items: center; justify-content: center; gap: 0.5rem;
+      padding: 0.5rem; background: #f1f5f9; border-bottom: 1px solid #e2e8f0;
+    }
+    .pm-pdf-controls button {
+      padding: 0.3rem 0.6rem; border: 1px solid #cbd5e1; border-radius: 0.25rem;
+      background: white; cursor: pointer; font-size: 0.8rem; min-height: 36px; min-width: 36px;
+    }
+    .pm-pdf-controls button:disabled { opacity: 0.4; cursor: default; }
+    .pm-canvas-wrap { display: flex; justify-content: center; padding: 0.5rem; min-height: 300px; overflow: auto; }
+    .pm-canvas-wrap canvas { max-width: 100%; height: auto; }
+    /* Image in preview modal */
+    .pm-img-controls {
+      display: flex; align-items: center; justify-content: center; gap: 0.5rem;
+      padding: 0.5rem; background: #f1f5f9; border-bottom: 1px solid #e2e8f0;
+    }
+    .pm-img-controls button {
+      padding: 0.3rem 0.6rem; border: 1px solid #cbd5e1; border-radius: 0.25rem;
+      background: white; cursor: pointer; font-size: 0.85rem; min-height: 36px; min-width: 36px;
+    }
+    .pm-img-wrap {
+      display: flex; justify-content: center; align-items: center;
+      overflow: auto; cursor: grab; flex: 1; padding: 0.5rem; background: #525659;
+    }
+    .pm-img-wrap.dragging { cursor: grabbing; }
+    .pm-img-wrap img { transition: transform 0.15s ease; max-width: 100%; height: auto; }
+    /* Text in preview modal */
+    .pm-text-content {
+      background: #1e293b; color: #e2e8f0; padding: 1rem; font-family: 'SFMono-Regular', Consolas, monospace;
+      font-size: 0.82rem; line-height: 1.65; min-height: 300px; white-space: pre-wrap; word-break: break-word;
+      tab-size: 4;
+    }
+    .pm-line-number {
+      display: inline-block; width: 3.5em; color: #64748b; text-align: right;
+      margin-right: 1em; user-select: none; font-size: 0.75rem;
+    }
   </style>
 {% endblock %}
 
@@ -582,6 +661,9 @@
           <td>{{ file.created_at.strftime('%Y-%m-%d %H:%M:%S') if file.created_at else 'N/A' }}</td>
           <td>
             <div style="display: flex; align-items: center;">
+              <button onclick="openPreviewModal({{ file.id }}, '{{ file.mime_type or '' }}', '{{ file.original_filename | e }}', event)" class="action-btn" title="Quick preview" aria-label="Preview {{ file.original_filename }}" style="min-height:44px;min-width:44px;">
+                <i class="fas fa-eye" aria-hidden="true"></i>
+              </button>
               <button onclick="viewFileDetail({{ file.id }}, event)" class="action-btn" title="View details" aria-label="View details for {{ file.original_filename }}" style="min-height:44px;min-width:44px;">
                 <i class="fas fa-info-circle" aria-hidden="true"></i>
               </button>
@@ -621,6 +703,9 @@
         <div class="flex flex-col items-end gap-2 flex-shrink-0">
           <span class="status-badge status-{{ file.processing_status }}">{{ file.processing_status | title }}</span>
           <div class="flex gap-1" role="group" aria-label="File actions" onclick="event.stopPropagation();" onkeydown="event.stopPropagation();">
+            <button onclick="openPreviewModal({{ file.id }}, '{{ file.mime_type or '' }}', '{{ file.original_filename | e }}', event)" class="action-btn" title="Quick preview" aria-label="Preview {{ file.original_filename }}" style="min-height:44px;min-width:44px;">
+              <i class="fas fa-eye" aria-hidden="true"></i>
+            </button>
             <button onclick="viewFileDetail({{ file.id }}, event)" class="action-btn" title="View details" aria-label="View details for {{ file.original_filename }}" style="min-height:44px;min-width:44px;">
               <i class="fas fa-info-circle" aria-hidden="true"></i>
             </button>
@@ -676,6 +761,24 @@
     </div>
   </div>
 
+  <!-- Preview side-panel modal -->
+  <div id="previewOverlay" class="preview-overlay" role="dialog" aria-modal="true" aria-labelledby="previewTitle">
+    <div class="preview-panel">
+      <div class="preview-panel-header">
+        <h3 id="previewTitle">Preview</h3>
+        <button class="preview-panel-close" onclick="closePreviewModal()" aria-label="Close preview">
+          <i class="fas fa-times" aria-hidden="true"></i>
+        </button>
+      </div>
+      <div class="preview-panel-body" id="previewBody" aria-live="polite">
+        <div style="display:flex;align-items:center;justify-content:center;height:100%;color:#9ca3af;">
+          <i class="fas fa-spinner fa-spin" aria-hidden="true" style="font-size:2rem;"></i>
+        </div>
+      </div>
+      <div class="preview-panel-footer" id="previewFooter"></div>
+    </div>
+  </div>
+
   <script>
     // Modal functionality
     const deleteModal = document.getElementById('deleteModal');
@@ -694,6 +797,184 @@
       window.location.href = `/files/${fileId}/detail`;
     }
 
+    // ── Preview modal ──
+    let _pmPdf = { doc: null, page: 1, total: 0 };
+    let _pmImgScale = 1;
+
+    function openPreviewModal(fileId, mime, filename, event) {
+      if (event) event.stopPropagation();
+      const overlay = document.getElementById('previewOverlay');
+      const title = document.getElementById('previewTitle');
+      const body = document.getElementById('previewBody');
+      const footer = document.getElementById('previewFooter');
+      title.textContent = filename || 'Preview';
+      body.innerHTML = '<div style="display:flex;align-items:center;justify-content:center;height:300px;color:#9ca3af;"><i class="fas fa-spinner fa-spin" style="font-size:2rem;"></i></div>';
+      footer.innerHTML = '';
+      _pmPdf = { doc: null, page: 1, total: 0 };
+      _pmImgScale = 1;
+      overlay.classList.add('active');
+      document.body.style.overflow = 'hidden';
+
+      footer.innerHTML =
+        `<a href="/files/${fileId}" aria-label="Open full view"><i class="fas fa-expand" aria-hidden="true"></i> Full view</a>` +
+        `<a href="/api/files/${fileId}/download?version=processed" aria-label="Download file"><i class="fas fa-download" aria-hidden="true"></i> Download</a>`;
+
+      // Try "processed" first; fall back to "original" on 404
+      _pmLoadPreview(body, fileId, mime, filename, 'processed');
+    }
+
+    function _pmLoadPreview(body, fileId, mime, filename, version) {
+      const previewUrl = `/api/files/${fileId}/preview?version=${version}`;
+      if (mime && mime.startsWith('image/')) {
+        _pmRenderImage(body, previewUrl, filename);
+      } else if (mime && mime.startsWith('text/')) {
+        _pmRenderText(body, previewUrl, function() {
+          if (version === 'processed') _pmLoadPreview(body, fileId, mime, filename, 'original');
+        });
+      } else {
+        _pmRenderPdf(body, previewUrl, function() {
+          if (version === 'processed') _pmLoadPreview(body, fileId, mime, filename, 'original');
+        });
+      }
+    }
+
+    function closePreviewModal() {
+      const overlay = document.getElementById('previewOverlay');
+      overlay.classList.remove('active');
+      document.body.style.overflow = '';
+      _pmPdf = { doc: null, page: 1, total: 0 };
+    }
+
+    // PDF rendering inside preview modal
+    function _pmRenderPdf(body, url, onError) {
+      body.innerHTML =
+        '<div class="pm-pdf-controls">' +
+          '<button onclick="_pmPdfPage(-1)" id="pm-prev" aria-label="Previous page"><i class="fas fa-chevron-left" aria-hidden="true"></i></button>' +
+          '<span id="pm-page-info" style="font-size:0.8rem;min-width:100px;text-align:center;">Loading…</span>' +
+          '<button onclick="_pmPdfPage(1)" id="pm-next" aria-label="Next page"><i class="fas fa-chevron-right" aria-hidden="true"></i></button>' +
+        '</div>' +
+        '<div class="pm-canvas-wrap" id="pm-canvas-wrap"><div style="text-align:center;padding:3rem;color:#94a3b8;"><i class="fas fa-spinner fa-spin" style="font-size:2rem;"></i></div></div>';
+
+      pdfjsLib.getDocument(url).promise.then(function(pdf) {
+        _pmPdf.doc = pdf;
+        _pmPdf.total = pdf.numPages;
+        _pmPdf.page = 1;
+        _pmPdfRender();
+      }).catch(function() {
+        if (onError) { onError(); return; }
+        document.getElementById('pm-canvas-wrap').innerHTML = '<div style="text-align:center;padding:2rem;color:#f87171;"><i class="fas fa-exclamation-triangle" style="font-size:2rem;margin-bottom:0.5rem;"></i><p>Failed to load PDF</p></div>';
+      });
+    }
+
+    function _pmPdfRender() {
+      var wrap = document.getElementById('pm-canvas-wrap');
+      if (!_pmPdf.doc || !wrap) return;
+      _pmPdf.doc.getPage(_pmPdf.page).then(function(page) {
+        var vp = page.getViewport({ scale: 1.0 });
+        var scale = Math.min((wrap.clientWidth - 16) / vp.width, 2.0);
+        var svp = page.getViewport({ scale: scale });
+        var canvas = document.createElement('canvas');
+        canvas.width = svp.width;
+        canvas.height = svp.height;
+        canvas.style.maxWidth = '100%';
+        canvas.style.height = 'auto';
+        wrap.innerHTML = '';
+        wrap.appendChild(canvas);
+        page.render({ canvasContext: canvas.getContext('2d'), viewport: svp });
+        _pmPdfUpdateInfo();
+      });
+    }
+
+    function _pmPdfPage(delta) {
+      var np = _pmPdf.page + delta;
+      if (np >= 1 && np <= _pmPdf.total) { _pmPdf.page = np; _pmPdfRender(); }
+    }
+
+    function _pmPdfUpdateInfo() {
+      var info = document.getElementById('pm-page-info');
+      if (info) info.textContent = 'Page ' + _pmPdf.page + ' of ' + _pmPdf.total;
+      var prev = document.getElementById('pm-prev');
+      var next = document.getElementById('pm-next');
+      if (prev) prev.disabled = _pmPdf.page <= 1;
+      if (next) next.disabled = _pmPdf.page >= _pmPdf.total;
+    }
+
+    // Image rendering inside preview modal
+    function _pmRenderImage(body, url, alt) {
+      body.innerHTML =
+        '<div class="pm-img-controls">' +
+          '<button onclick="_pmImgZoom(1.25)" title="Zoom in" aria-label="Zoom in"><i class="fas fa-search-plus" aria-hidden="true"></i></button>' +
+          '<button onclick="_pmImgZoom(0.8)" title="Zoom out" aria-label="Zoom out"><i class="fas fa-search-minus" aria-hidden="true"></i></button>' +
+          '<button onclick="_pmImgReset()" title="Reset" aria-label="Reset zoom"><i class="fas fa-expand" aria-hidden="true"></i></button>' +
+          '<span id="pm-zoom-level" style="font-size:0.8rem;color:#6b7280;">100%</span>' +
+        '</div>' +
+        '<div class="pm-img-wrap" id="pm-img-wrap"><img id="pm-preview-img" src="' + url + '" alt="' + (alt || 'Preview') + '" draggable="false" style="max-width:100%;height:auto;"></div>';
+      // Drag-pan
+      var wrap = document.getElementById('pm-img-wrap');
+      if (wrap) {
+        var dragging = false, sX, sY, sL, sT;
+        wrap.addEventListener('mousedown', function(e){ dragging=true; wrap.classList.add('dragging'); sX=e.pageX-wrap.offsetLeft; sY=e.pageY-wrap.offsetTop; sL=wrap.scrollLeft; sT=wrap.scrollTop; });
+        wrap.addEventListener('mousemove', function(e){ if(!dragging) return; e.preventDefault(); wrap.scrollLeft=sL-(e.pageX-wrap.offsetLeft-sX); wrap.scrollTop=sT-(e.pageY-wrap.offsetTop-sY); });
+        wrap.addEventListener('mouseup', function(){ dragging=false; wrap.classList.remove('dragging'); });
+        wrap.addEventListener('mouseleave', function(){ dragging=false; wrap.classList.remove('dragging'); });
+        wrap.addEventListener('wheel', function(e){ e.preventDefault(); _pmImgZoom(e.deltaY<0?1.1:0.9); }, {passive:false});
+      }
+    }
+
+    function _pmImgZoom(factor) {
+      _pmImgScale = Math.max(0.25, Math.min(5, _pmImgScale * factor));
+      var img = document.getElementById('pm-preview-img');
+      if (img) img.style.transform = 'scale(' + _pmImgScale + ')';
+      var lbl = document.getElementById('pm-zoom-level');
+      if (lbl) lbl.textContent = Math.round(_pmImgScale * 100) + '%';
+    }
+
+    function _pmImgReset() {
+      _pmImgScale = 1;
+      var img = document.getElementById('pm-preview-img');
+      if (img) img.style.transform = 'scale(1)';
+      var lbl = document.getElementById('pm-zoom-level');
+      if (lbl) lbl.textContent = '100%';
+    }
+
+    // Text rendering inside preview modal
+    function _pmRenderText(body, url, onError) {
+      body.innerHTML = '<div class="pm-text-content" id="pm-text-content"><div style="text-align:center;padding:2rem;color:#94a3b8;"><i class="fas fa-spinner fa-spin"></i> Loading…</div></div>';
+      fetch(url)
+        .then(function(r) { if (!r.ok) throw new Error('HTTP ' + r.status); return r.text(); })
+        .then(function(text) {
+          var container = document.getElementById('pm-text-content');
+          if (!container) return;
+          container.innerHTML = '';
+          var lines = text.split('\n');
+          for (var i = 0; i < lines.length; i++) {
+            var div = document.createElement('div');
+            var num = document.createElement('span');
+            num.className = 'pm-line-number';
+            num.textContent = (i + 1) + '';
+            div.appendChild(num);
+            div.appendChild(document.createTextNode(lines[i]));
+            container.appendChild(div);
+          }
+        })
+        .catch(function() {
+          if (onError) { onError(); return; }
+          var c = document.getElementById('pm-text-content');
+          if (c) c.innerHTML = '<div style="color:#f87171;padding:1rem;">Failed to load file</div>';
+        });
+    }
+
+    // Close preview on overlay click or Escape
+    document.getElementById('previewOverlay').addEventListener('click', function(e) {
+      if (e.target === this) closePreviewModal();
+    });
+    document.addEventListener('keydown', function(e) {
+      if (e.key === 'Escape') {
+        var overlay = document.getElementById('previewOverlay');
+        if (overlay && overlay.classList.contains('active')) closePreviewModal();
+      }
+    });
+
     cancelDelete.addEventListener('click', () => {
       deleteModal.style.display = 'none';
     });
diff --git a/tests/test_document_preview.py b/tests/test_document_preview.py
new file mode 100644
index 00000000..45e46c3c
--- /dev/null
+++ b/tests/test_document_preview.py
@@ -0,0 +1,413 @@
+"""
+Tests for in-browser document preview functionality.
+
+Tests the pdf.js-based PDF viewer, image zoom/pan, text preview with
+line numbers, and the file-list preview modal introduced by the
+in-browser document preview feature.
+"""
+
+import os
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.models import FileRecord
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _create_file_record(
+    db_session,
+    *,
+    filename: str = "test.pdf",
+    mime_type: str = "application/pdf",
+    file_path: str,
+    processed_path: str | None = None,
+) -> FileRecord:
+    """Create and persist a FileRecord for testing."""
+    rec = FileRecord(
+        filehash="hash_" + filename,
+        original_filename=filename,
+        local_filename=file_path,
+        original_file_path=file_path,
+        processed_file_path=processed_path,
+        file_size=os.path.getsize(file_path) if os.path.exists(file_path) else 1024,
+        mime_type=mime_type,
+    )
+    db_session.add(rec)
+    db_session.commit()
+    db_session.refresh(rec)
+    return rec
+
+
+# ===========================================================================
+# file_view.html – PDF preview via pdf.js
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFileViewPdfJs:
+    """file_view.html should embed a pdf.js viewer for PDF files."""
+
+    def test_pdf_file_renders_pdfjs_viewer(self, client: TestClient, db_session, tmp_path):
+        """PDF file view should include pdf.js library and canvas-based viewer."""
+        pdf = tmp_path / "doc.pdf"
+        pdf.write_bytes(b"%PDF-1.4 test")
+        rec = _create_file_record(db_session, file_path=str(pdf), mime_type="application/pdf")
+
+        response = client.get(f"/files/{rec.id}")
+        assert response.status_code == 200
+        html = response.text
+
+        # pdf.js library must be loaded
+        assert "pdf.min.js" in html
+        assert "pdf.worker.min.js" in html
+
+        # pdf.js canvas wrapper and page controls must be present
+        assert 'id="pdf-viewer"' in html
+        assert 'id="pdf-canvas-wrap"' in html
+        assert 'id="pdf-page-info"' in html
+        assert "pdfInit(" in html
+
+        # Should NOT have an iframe in the preview section
+        assert 'id="pdf-viewer"' in html
+
+    def test_pdf_file_no_iframe(self, client: TestClient, db_session, tmp_path):
+        """PDF should not use native iframe-based preview."""
+        pdf = tmp_path / "doc2.pdf"
+        pdf.write_bytes(b"%PDF-1.4 test")
+        rec = _create_file_record(db_session, file_path=str(pdf), mime_type="application/pdf")
+
+        response = client.get(f"/files/{rec.id}")
+        html = response.text
+
+        # The preview section should use pdf-viewer, not iframe
+        assert 'id="pdf-viewer"' in html
+        assert "pdf-canvas-wrap" in html
+
+    def test_page_navigation_controls(self, client: TestClient, db_session, tmp_path):
+        """PDF viewer should have previous/next page buttons."""
+        pdf = tmp_path / "nav.pdf"
+        pdf.write_bytes(b"%PDF-1.4 test")
+        rec = _create_file_record(db_session, file_path=str(pdf), mime_type="application/pdf")
+
+        response = client.get(f"/files/{rec.id}")
+        html = response.text
+
+        assert 'id="pdf-prev-btn"' in html
+        assert 'id="pdf-next-btn"' in html
+        assert "pdfChangePage" in html
+
+
+# ===========================================================================
+# file_view.html – Image preview with zoom / pan
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFileViewImagePreview:
+    """file_view.html should show an image viewer with zoom/pan for image files."""
+
+    def test_image_file_renders_image_viewer(self, client: TestClient, db_session, tmp_path):
+        """Image files should show zoom/pan controls instead of iframe."""
+        img = tmp_path / "photo.jpg"
+        img.write_bytes(b"\xff\xd8\xff\xe0" + b"\x00" * 100)  # minimal JPEG header
+        rec = _create_file_record(db_session, filename="photo.jpg", mime_type="image/jpeg", file_path=str(img))
+
+        response = client.get(f"/files/{rec.id}")
+        assert response.status_code == 200
+        html = response.text
+
+        assert 'id="img-viewer"' in html
+        assert 'id="preview-img"' in html
+        assert 'id="img-wrap"' in html
+        assert "imgZoom" in html
+        assert "imgReset" in html
+
+    def test_image_zoom_controls(self, client: TestClient, db_session, tmp_path):
+        """Image viewer should have zoom in, zoom out, and reset controls."""
+        img = tmp_path / "photo.png"
+        img.write_bytes(b"\x89PNG\r\n\x1a\n" + b"\x00" * 50)
+        rec = _create_file_record(db_session, filename="photo.png", mime_type="image/png", file_path=str(img))
+
+        response = client.get(f"/files/{rec.id}")
+        html = response.text
+
+        assert 'aria-label="Zoom in"' in html
+        assert 'aria-label="Zoom out"' in html
+        assert 'aria-label="Reset zoom"' in html
+        assert 'id="img-zoom-level"' in html
+
+    def test_image_pan_support(self, client: TestClient, db_session, tmp_path):
+        """Image viewer should support mouse-drag panning."""
+        img = tmp_path / "wide.webp"
+        img.write_bytes(b"RIFF" + b"\x00" * 50)
+        rec = _create_file_record(db_session, filename="wide.webp", mime_type="image/webp", file_path=str(img))
+
+        response = client.get(f"/files/{rec.id}")
+        html = response.text
+
+        # Pan support is implemented via JavaScript on img-wrap
+        assert "mousedown" in html
+        assert "mousemove" in html
+        assert "cursor: grab" in html or "cursor:grab" in html
+
+
+# ===========================================================================
+# file_view.html – Text file preview with line numbers
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFileViewTextPreview:
+    """file_view.html should show a text viewer with line numbers for text files."""
+
+    def test_text_file_renders_text_viewer(self, client: TestClient, db_session, tmp_path):
+        """Text files should show the text-viewer component."""
+        txt = tmp_path / "readme.txt"
+        txt.write_text("Hello world\nSecond line\n")
+        rec = _create_file_record(db_session, filename="readme.txt", mime_type="text/plain", file_path=str(txt))
+
+        response = client.get(f"/files/{rec.id}")
+        assert response.status_code == 200
+        html = response.text
+
+        assert 'id="text-viewer"' in html
+        assert 'id="text-preview-content"' in html
+        assert "loadTextPreview" in html
+
+    def test_text_viewer_has_copy_button(self, client: TestClient, db_session, tmp_path):
+        """Text viewer should have a Copy button."""
+        txt = tmp_path / "code.py"
+        txt.write_text("print('hello')\n")
+        rec = _create_file_record(db_session, filename="code.py", mime_type="text/x-python", file_path=str(txt))
+
+        response = client.get(f"/files/{rec.id}")
+        html = response.text
+
+        assert "copyTextPreview" in html
+        assert 'id="text-copy-btn"' in html
+
+    def test_text_viewer_line_numbers(self, client: TestClient, db_session, tmp_path):
+        """Text viewer JS should generate line numbers."""
+        txt = tmp_path / "data.csv"
+        txt.write_text("a,b,c\n1,2,3\n")
+        rec = _create_file_record(db_session, filename="data.csv", mime_type="text/csv", file_path=str(txt))
+
+        response = client.get(f"/files/{rec.id}")
+        html = response.text
+
+        # JS builds line-number spans
+        assert "line-number" in html
+
+
+# ===========================================================================
+# file_view.html – Preview icon adapts to MIME type
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFileViewPreviewIcon:
+    """Preview card icon should match the MIME type of the file."""
+
+    def test_pdf_icon(self, client: TestClient, db_session, tmp_path):
+        """PDF files show a file-pdf icon."""
+        pdf = tmp_path / "a.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        rec = _create_file_record(db_session, file_path=str(pdf), mime_type="application/pdf")
+
+        html = client.get(f"/files/{rec.id}").text
+        assert "fa-file-pdf" in html
+
+    def test_image_icon(self, client: TestClient, db_session, tmp_path):
+        """Image files show an image icon."""
+        img = tmp_path / "p.jpg"
+        img.write_bytes(b"\xff\xd8\xff\xe0" + b"\x00" * 10)
+        rec = _create_file_record(db_session, filename="p.jpg", mime_type="image/jpeg", file_path=str(img))
+
+        html = client.get(f"/files/{rec.id}").text
+        assert "fa-image" in html
+
+    def test_text_icon(self, client: TestClient, db_session, tmp_path):
+        """Text files show a code icon."""
+        txt = tmp_path / "t.txt"
+        txt.write_text("hello")
+        rec = _create_file_record(db_session, filename="t.txt", mime_type="text/plain", file_path=str(txt))
+
+        html = client.get(f"/files/{rec.id}").text
+        assert "fa-file-code" in html
+
+
+# ===========================================================================
+# files.html – Preview modal from file list
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFilesPreviewModal:
+    """files.html should include a preview side-panel triggered from the file list."""
+
+    def test_preview_modal_markup(self, client: TestClient, db_session, tmp_path):
+        """Files page should contain the preview overlay HTML."""
+        pdf = tmp_path / "list.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        _create_file_record(db_session, file_path=str(pdf))
+
+        response = client.get("/files")
+        assert response.status_code == 200
+        html = response.text
+
+        assert 'id="previewOverlay"' in html
+        assert 'id="previewBody"' in html
+        assert 'id="previewTitle"' in html
+        assert 'role="dialog"' in html
+        assert 'aria-modal="true"' in html
+
+    def test_preview_button_in_actions(self, client: TestClient, db_session, tmp_path):
+        """Each file row should have a preview (eye) button."""
+        pdf = tmp_path / "btn.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        _create_file_record(db_session, file_path=str(pdf))
+
+        html = client.get("/files").text
+        assert "openPreviewModal" in html
+        assert "fa-eye" in html
+
+    def test_preview_modal_has_pdfjs(self, client: TestClient, db_session, tmp_path):
+        """Files page should load pdf.js for the preview modal."""
+        pdf = tmp_path / "js.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        _create_file_record(db_session, file_path=str(pdf))
+
+        html = client.get("/files").text
+        assert "pdf.min.js" in html
+        assert "pdfjsLib" in html
+
+    def test_preview_modal_close(self, client: TestClient, db_session, tmp_path):
+        """Preview modal should have a close button and Escape handler."""
+        pdf = tmp_path / "close.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        _create_file_record(db_session, file_path=str(pdf))
+
+        html = client.get("/files").text
+        assert "closePreviewModal" in html
+        assert "Escape" in html
+
+    def test_preview_modal_footer_links(self, client: TestClient, db_session, tmp_path):
+        """Preview modal JS should include download and full-view links."""
+        pdf = tmp_path / "footer.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        _create_file_record(db_session, file_path=str(pdf))
+
+        html = client.get("/files").text
+        assert "Full view" in html
+        assert "Download" in html
+
+
+# ===========================================================================
+# file_detail.html – Bottom preview section uses correct variable names
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFileDetailBottomPreview:
+    """file_detail.html bottom File Previews card should render when files exist."""
+
+    def test_bottom_preview_card_renders(self, client: TestClient, db_session, tmp_path):
+        """Bottom 'File Previews' card should display when file exists on disk."""
+        pdf = tmp_path / "detail.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        rec = _create_file_record(db_session, file_path=str(pdf), processed_path=str(pdf))
+
+        response = client.get(f"/files/{rec.id}/detail")
+        assert response.status_code == 200
+        html = response.text
+
+        # The fixed section should now render (was previously using wrong variable names)
+        assert "File Previews" in html
+        assert "Original File" in html or "Processed File" in html
+
+    def test_bottom_preview_has_download_link(self, client: TestClient, db_session, tmp_path):
+        """Bottom preview card should have download links."""
+        pdf = tmp_path / "dl.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        rec = _create_file_record(db_session, file_path=str(pdf), processed_path=str(pdf))
+
+        response = client.get(f"/files/{rec.id}/detail")
+        html = response.text
+        assert f"/api/files/{rec.id}/download" in html
+
+    def test_image_preview_in_detail(self, client: TestClient, db_session, tmp_path):
+        """Image files should render an <img> tag in the bottom preview card."""
+        img = tmp_path / "detail_img.jpg"
+        img.write_bytes(b"\xff\xd8\xff\xe0" + b"\x00" * 100)
+        rec = _create_file_record(
+            db_session,
+            filename="detail_img.jpg",
+            mime_type="image/jpeg",
+            file_path=str(img),
+        )
+
+        response = client.get(f"/files/{rec.id}/detail")
+        html = response.text
+        assert f"/api/files/{rec.id}/preview?version=original" in html
+
+
+# ===========================================================================
+# Existing OCR text functionality preserved
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFileViewOcrText:
+    """Verify that the existing OCR text feature still works after the preview upgrade."""
+
+    def test_ocr_text_toggle_present(self, client: TestClient, db_session, tmp_path):
+        """Pages with ocr_text should still have the toggle button."""
+        pdf = tmp_path / "ocr.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        rec = _create_file_record(db_session, file_path=str(pdf))
+        rec.ocr_text = "Sample extracted OCR text content"
+        db_session.commit()
+
+        html = client.get(f"/files/{rec.id}").text
+        assert "toggleOcrText" in html
+        assert "ocr-text-block" in html
+        assert "Sample extracted OCR text content" in html
+
+    def test_text_extraction_button(self, client: TestClient, db_session, tmp_path):
+        """Pages without ocr_text but with files should show extract button."""
+        pdf = tmp_path / "no_ocr.pdf"
+        pdf.write_bytes(b"%PDF-1.4")
+        rec = _create_file_record(db_session, file_path=str(pdf))
+
+        html = client.get(f"/files/{rec.id}").text
+        assert "loadText" in html or "Extract" in html
+
+
+# ===========================================================================
+# No file available fallback
+# ===========================================================================
+
+
+@pytest.mark.unit
+class TestFileViewNoFile:
+    """When no file is on disk, a fallback message should display."""
+
+    def test_no_preview_fallback(self, client: TestClient, db_session):
+        """No-file-on-disk scenario shows a fallback message."""
+        rec = FileRecord(
+            filehash="nope",
+            original_filename="gone.pdf",
+            local_filename="/nonexistent/gone.pdf",
+            file_size=0,
+            mime_type="application/pdf",
+        )
+        db_session.add(rec)
+        db_session.commit()
+        db_session.refresh(rec)
+
+        html = client.get(f"/files/{rec.id}").text
+        assert "No file available for preview" in html