Stay Upright by HoshiNoNaiGinga

In fullscreen, Firefox for Android forces landscape. But a lot of "vertical" videos are actually landscape files with the 9:16 content centred and black bars on the sides — so they end up as a small rectangle in the middle of your screen, and rotating the phone does nothing.

Stay Upright lets you decide, with the most natural gesture there is: you straighten the phone.

HOW IT WORKS
- Straighten the phone for about a second during a fullscreen video: it switches to portrait and zooms into the centred 9:16 content.
- Turn it back on its side: back to landscape.
- Files that are already vertical go portrait right away, no sensor needed.

The trigger only arms once the phone has been seen on its side, so it never fires the moment you enter fullscreen.

GESTURES (in every orientation)
- Pinch: zoom towards the point between your fingers
- One finger: pan the framing, bounded by the edges of the video
- Double tap: toggle fit / fill

Zoom settings last for the current video only — every new fullscreen starts from "fit".

PRIVACY
No permissions, no background page, no network requests, nothing collected. The motion sensor is read only while a video is in fullscreen.

GOOD TO KNOW
- Built for Firefox for Android. On desktop Firefox the gestures still work on a touchscreen, but automatic rotation does not (desktop Firefox keeps orientation locking disabled by default).
- DRM-protected video can't be zoomed: the browser doesn't allow those frames to be transformed.
- On players that put their own container into fullscreen, their one-finger gestures may compete with panning.

Two files, no dependencies, no tracking.