diff --git a/src/components/EditorCanvas/Canvas.jsx b/src/components/EditorCanvas/Canvas.jsx
index 8a6a9ad4f..1b6bf34e8 100644
--- a/src/components/EditorCanvas/Canvas.jsx
+++ b/src/components/EditorCanvas/Canvas.jsx
@@ -699,12 +699,18 @@ export default function Canvas() {
           },
           zoom: e.deltaY <= 0 ? prev.zoom * 1.05 : prev.zoom / 1.05,
         }));
-      } else if (e.shiftKey) {
+      } else if (e.shiftKey || e.deltaX !== 0) {
+        // Browsers disagree about where a horizontal scroll arrives. Chrome
+        // translates shift + wheel into deltaX and leaves deltaY at 0, so
+        // reading deltaY alone added nothing and the diagram did not move.
+        // Firefox keeps it on deltaY with shiftKey set. A trackpad or a tilt
+        // wheel sends deltaX with no modifier at all.
+        const horizontal = e.deltaX !== 0 ? e.deltaX : e.deltaY;
         setTransform((prev) => ({
           ...prev,
           pan: {
             ...prev.pan,
-            x: prev.pan.x + e.deltaY / prev.zoom,
+            x: prev.pan.x + horizontal / prev.zoom,
           },
         }));
       } else {