Twitch Vertical Toggle от MarentDev

Some Twitch streams are also broadcast in a vertical 9:16 format for the mobile app, but the desktop website never gives you access to it. This extension adds a button to the player controls to switch between the vertical feed and the usual horizontal one.

HOW IT WORKS
The Twitch player requests a playback token describing which feed it wants, then loads the matching stream playlist. The extension asks for the vertical feed and keeps only the matching video renditions in that playlist, so the player cannot silently fall back to the
16:9 version. Switching back restores the horizontal feed the same way.

FEATURES
• A single button in the player controls, next to the settings gear
• Per-channel preference: vertical on one streamer, normal on another
• Automatic detection: the button announces when a stream offers a vertical feed, and is greyed out with an explanation when it does not
• Works on twitch.tv, the popout player and player.twitch.tv embeds
• Switches in place, without reloading the page, whenever the player allows it
• English and French interface

GOOD TO KNOW
• Only streams that the creator actually broadcasts in vertical can be switched. The
extension cannot create a vertical feed that does not exist — when there is none, the button says so and stays inactive.
• A vertical video is displayed centred in the 16:9 player, with black bars on each side.

PRIVACY
No account, no data collection, no analytics, no remote code. The extension declares no permission at all and only runs on twitch.tv pages, entirely inside your browser.