Ultra Zoom vs. Firefox built-in zoom
Firefox has the strongest built-in zoom of any major browser — per-site memory, separate text-only mode, accessible toolbar controls. What it doesn’t have is hover-to-zoom on individual images. That’s the gap Ultra Zoom fills, with a signed Firefox add-on built on the modern WebExtensions platform.
How each one actually works
- Firefox built-in zoom — scales the whole page, with optional text-only mode. Per-site zoom levels persist. Useful for reading; doesn’t reach the source image. Deep dive on browser-native zoom.
- Ultra Zoom for Firefox — hover an image, see the full-resolution source as an overlay. Theater mode, gallery navigation, reverse image search, and on-device AI upscaling. Same codebase as the Chrome build.
The Firefox hover-zoom story
Firefox users have had a rough decade with hover-zoom. Thumbnail Zoom Plus broke when legacy add-ons retired. Imagus has had Manifest V3 hiccups. Hover Zoom Plus and most forks are Chrome-first. Ultra Zoom is one of the few extensions still treating Firefox as a first-class target — signed, current, same release cadence as the Chrome build.
Side by side
| Feature | Firefox built-in | Ultra Zoom for Firefox |
|---|---|---|
| Per-site page zoom level | ✓ | – |
| Text-only zoom mode | ✓ | – |
| Hover-to-zoom on every site | – | ✓ |
| Loads full-resolution source image | – | ✓ |
| Site-specific plugins | – | ✓ |
| Theater mode & gallery navigation | – | ✓ |
| Reverse image search shortcuts | – | ✓ |
| On-device AI upscaling | – | ✓ (Pro) |
| Zero telemetry | ✓ | ✓ |
Install on Firefox
The core extension is free forever. Pro is a 7-day free trial when you’re ready — see plans.