diff --git a/index.html b/index.html
index 113a9a1..a351652 100644
--- a/index.html
+++ b/index.html
@@ -177,6 +177,12 @@ let currentLibrary = null;
 let currentFolder = null; // null = all
 let currentImageId = null;
 
+// --- Virtual scroller state ---
+const OVERSCAN = 2; // extra rows to render above/below viewport
+let vCols = 1;
+let vRowHeight = 0;
+let vScrollRAF = null;
+
 // Init: load library list
 async function init() {
   const res = await fetch('/api/libraries');
@@ -274,6 +280,7 @@ function filterImages() {
 function renderGrid() {
   const grid = document.getElementById('grid');
   const empty = document.getElementById('empty');
+  const container = document.getElementById('grid-container');
   const stats = document.getElementById('stats');
   stats.textContent = `${filteredImages.length} items`;
 
@@ -286,35 +293,95 @@ function renderGrid() {
 
   empty.style.display = 'none';
   grid.style.display = 'grid';
-  grid.innerHTML = '';
+  container.scrollTop = 0;
 
-  filteredImages.forEach(img => {
-    const card = document.createElement('div');
-    card.className = 'card';
-    card.onclick = () => openLightbox(img);
+  // Measure column count and row height from CSS grid
+  // We do one measurement pass with a dummy card first
+  function measureGrid() {
+    const thumbSize = parseInt(getComputedStyle(document.documentElement).getPropertyValue('--thumb-size')) || 180;
+    const gridWidth = grid.clientWidth || container.clientWidth - 32;
+    vCols = Math.max(1, Math.floor((gridWidth + 12) / (thumbSize + 12)));
+    // Card height: thumb aspect 16/10 + info ~60px
+    vRowHeight = Math.round((thumbSize * 10 / 16)) + 62 + 12; // thumb-h + info + gap
+  }
+  measureGrid();
 
-    const thumbSrc = img._thumbnail
-      ? `/api/thumbnail/${currentLibrary}/${img.id}`
-      : null;
+  // Detach scroll listener before wiping grid
+  container.onscroll = null;
 
-    const extIcon = extToIcon(img.ext);
+  function renderVisible() {
+    measureGrid();
+    const totalRows = Math.ceil(filteredImages.length / vCols);
+    const totalHeight = totalRows * vRowHeight;
 
-    card.innerHTML = `
-      <div class="thumb-wrap">
-        ${thumbSrc
-          ? `<img src="${thumbSrc}" loading="lazy" alt="${escHtml(img.name)}" onerror="this.style.display='none';this.nextElementSibling.style.display='flex'">`
-          : ''}
-        <span class="thumb-placeholder" style="${thumbSrc ? 'display:none' : ''}">${extIcon}</span>
-        <span class="ext-badge">${img.ext || '?'}</span>
-      </div>
-      <div class="card-info">
-        <div class="card-name" title="${escHtml(img.name)}">${escHtml(img.name)}</div>
-        <div class="card-meta">${img.ext?.toUpperCase() || ''} ${img.duration ? '· ' + fmtDuration(img.duration) : ''}</div>
-        ${img.tags?.length ? `<div class="card-tags">${img.tags.map(t => `<span class="tag">${escHtml(t)}</span>`).join('')}</div>` : ''}
-      </div>
-    `;
-    grid.appendChild(card);
-  });
+    const scrollTop = container.scrollTop;
+    const viewHeight = container.clientHeight;
+
+    const firstVisRow = Math.max(0, Math.floor(scrollTop / vRowHeight) - OVERSCAN);
+    const lastVisRow = Math.min(totalRows - 1, Math.ceil((scrollTop + viewHeight) / vRowHeight) + OVERSCAN);
+
+    const firstIdx = firstVisRow * vCols;
+    const lastIdx = Math.min(filteredImages.length - 1, (lastVisRow + 1) * vCols - 1);
+
+    // Spacer above
+    const topH = firstVisRow * vRowHeight;
+    // Spacer below
+    const bottomH = Math.max(0, (totalRows - lastVisRow - 1) * vRowHeight);
+
+    grid.innerHTML = '';
+
+    // Top spacer
+    if (topH > 0) {
+      const spacer = document.createElement('div');
+      spacer.style.cssText = `grid-column: 1 / -1; height: ${topH}px; pointer-events: none;`;
+      grid.appendChild(spacer);
+    }
+
+    // Render only visible cards
+    for (let i = firstIdx; i <= lastIdx; i++) {
+      const img = filteredImages[i];
+      const card = document.createElement('div');
+      card.className = 'card';
+      card.onclick = () => openLightbox(img);
+
+      const thumbSrc = img._thumbnail ? `/api/thumbnail/${currentLibrary}/${img.id}` : null;
+      const extIcon = extToIcon(img.ext);
+
+      card.innerHTML = `
+        <div class="thumb-wrap">
+          ${thumbSrc
+            ? `<img src="${thumbSrc}" alt="${escHtml(img.name)}" onerror="this.style.display='none';this.nextElementSibling.style.display='flex'">`
+            : ''}
+          <span class="thumb-placeholder" style="${thumbSrc ? 'display:none' : ''}">${extIcon}</span>
+          <span class="ext-badge">${img.ext || '?'}</span>
+        </div>
+        <div class="card-info">
+          <div class="card-name" title="${escHtml(img.name)}">${escHtml(img.name)}</div>
+          <div class="card-meta">${img.ext?.toUpperCase() || ''} ${img.duration ? '· ' + fmtDuration(img.duration) : ''}</div>
+          ${img.tags?.length ? `<div class="card-tags">${img.tags.map(t => `<span class="tag">${escHtml(t)}</span>`).join('')}</div>` : ''}
+        </div>
+      `;
+      grid.appendChild(card);
+    }
+
+    // Bottom spacer
+    if (bottomH > 0) {
+      const spacer = document.createElement('div');
+      spacer.style.cssText = `grid-column: 1 / -1; height: ${bottomH}px; pointer-events: none;`;
+      grid.appendChild(spacer);
+    }
+  }
+
+  renderVisible();
+
+  // Re-render on scroll (throttled via rAF)
+  container.onscroll = () => {
+    if (vScrollRAF) return;
+    vScrollRAF = requestAnimationFrame(() => {
+      vScrollRAF = null;
+      renderVisible();
+    });
+  };
 }
 
 function openLightbox(img) {
@@ -359,6 +426,7 @@ document.addEventListener('keydown', e => { if (e.key === 'Escape') closeLightbo
 
 function updateThumbSize(val) {
   document.documentElement.style.setProperty('--thumb-size', val + 'px');
+  if (filteredImages.length > 0) renderGrid();
 }
 
 function extToIcon(ext) {