Quickly inspect the rendered dimensions and aspect ratio of any HTML element directly within Firefox.
Perfect for developers, designers and QA engineers working with responsive layouts.
- 🔍 Inspect any HTML element by hovering over it
- 📐 View rendered width, height and aspect ratio instantly
- ➗ Automatically reduce ratios (e.g. 1920 × 1080 → 16:9)
- ⭐ Recognise common aspect ratios
- ✏️ Manual measurement mode for arbitrary regions
- ⚡ Lightweight with zero dependencies
- 🌐 Works on virtually any webpage
Install Aspect Inspector from the Firefox Add-ons store:
https://addons.mozilla.org/en-GB/firefox/addon/aspect-inspector/
- Click the Aspect Inspector toolbar button.
- Move your mouse over the page to inspect elements.
- Click an element to lock the current selection.
- While locked, click another element to retarget the selection.
- Click and drag anywhere on the page to create a manual measurement area.
- Press Esc or Space to clear the current lock.
- Press Esc again (when no element is locked) to exit inspection mode.
Aspect Inspector respects your privacy.
- No analytics
- No tracking
- No data collection
- No external network requests
- All processing happens locally within your browser
Aspect Inspector requests only the permissions required to function:
| Permission | Reason |
|---|---|
activeTab |
Allows inspection of the currently active tab after you activate the extension. |
scripting |
Injects the inspection script into the active page. |
Bug reports, feature requests and pull requests are always welcome.
If you find an issue or have an idea for an improvement, please open an issue on GitHub.
MIT © Stewart Zollinger