diff --git a/classifier/js/preview.js b/classifier/js/preview.js
index 4a39145..6f550ae 100644
--- a/classifier/js/preview.js
+++ b/classifier/js/preview.js
@@ -410,10 +410,18 @@
             const workbook = XLSX.read(arrayBuffer, { type: 'array' });
             
             container.innerHTML = '';
-            
+            // Make the content area a height-constrained flex column so the table
+            // scroller below fills the viewport — its horizontal scrollbar then
+            // sits at the window bottom instead of at the bottom of a tall sheet.
+            container.style.display = 'flex';
+            container.style.flexDirection = 'column';
+            container.style.minHeight = '0';
+            container.style.overflow = 'hidden';
+
             if (workbook.SheetNames.length > 1) {
                 const tabs = previewWindow.document.createElement('div');
                 tabs.className = 'sheet-tabs';
+                tabs.style.flexShrink = '0';
                 workbook.SheetNames.forEach((name, i) => {
                     const tab = previewWindow.document.createElement('button');
                     tab.className = 'sheet-tab' + (i === 0 ? ' active' : '');
@@ -430,6 +438,7 @@
             
             const tableContainer = previewWindow.document.createElement('div');
             tableContainer.style.flex = '1';
+            tableContainer.style.minHeight = '0';   // allow it to shrink so overflow scrolls
             tableContainer.style.overflow = 'auto';
             container.appendChild(tableContainer);