Best Universal Volume Booster lets you boost videos, streams, and audio past the normal 100% volume limit. Start playing something, click the extension, choose your boost level, and turn it on. You can boost compatible media up to 500%. It is made to work on whatever site you activate it on instead of being tied to one specific service. Features

Boost volume from 100% to 500%
Works with both video and audio
Only activates on the current site/tab when you use it
Auto-reapply option for sites that replace or reload their media player
Works with dynamically loaded videos, streams, and audio
Remembers your volume and auto-reapply settings locally
No analytics
No tracking
No account required
No personal data collection

Example sites Works with many sites that use normal HTML5 video or audio, including:

YouTube
Twitch
Vimeo
SoundCloud
Reddit
Kick
TikTok
Instagram
Facebook
X / Twitter
Netflix

It should also work on plenty of other sites using standard HTML5 media. How to use

Start playing a video, stream, or audio track.
Click Best Universal Volume Booster.
Pick your boost level.
Click Enable Boost.
Turn on Auto-reapply if the site keeps replacing or reloading its media player.

Going all the way to 500% can make already-loud audio distort, so lower the boost if that happens.

Privacy Best Universal Volume Booster does not collect or send personal data. The extension runs locally in Firefox. Your selected volume level and auto-reapply setting are only stored locally in your browser. Compatibility Some sites use DRM, protected media, custom players, or other restrictions that browser extensions cannot always access. Because of that, compatibility cannot be guaranteed on literally every website.