Source code: https://github.com/redubbledd1-ops/Fullscreen-Fill

No bundler, transpiler or minifier: tools/build.js copies the files unchanged and uses manifest.firefox.json as the manifest.

Changes since 1.23.2: only the popup/settings page (popup.html, popup.js, i18n.js). A "Reset all settings" button removes the extension's own keys from storage.sync so every setting falls back to its default. No new permissions, no changes to the content scripts.

New
- Zoom mode, now the default: the picture is enlarged until the screen is covered and the edges are cropped, so nothing is distorted. Stretch is still there as a choice.
- Stretch limit: stretch only up to a difference you pick (5-50%); beyond that the video is zoomed or keeps its bars.
- "Fill from": leave square or other narrow videos exactly as the site shows them.
- A settings page (Add-ons > Fullscreen Fill > Settings), also on Firefox for Android.
- Report a problem from the popup: you see the whole report and send it yourself, by email or as a GitHub issue. The site and technical details are only included if you tick them.
- The on/off switch now sits next to the title, and the popup says whether a video was stretched, zoomed or kept its bars, and why.

Fixed
- Flickering and black flashes when a video went fullscreen on phones (YouTube and other sites).
- Popup text was far too small on Firefox for Android.