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. Compatible media can be boosted up to 500%. Best Universal Volume Booster is designed to work across the web instead of being tied to one specific streaming service or website. Features

Boost volume from 100% to 500%
Works with both video and audio
Boosting only runs on tabs where you enable it
Supports media players embedded inside frames
Supports dynamically loaded and replaced media players
Supports media inside compatible Shadow DOM players
Auto-reapply option for sites that replace or reload their media player
Can detect multiple playing media elements on a page
Remembers your volume and auto-reapply settings locally
No analytics
No tracking
No account required
No personal data collection

Example sites Best Universal Volume Booster works with many sites that use compatible HTML5 video or audio, including:

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

It should also work on many other websites using standard HTML5 media. Compatibility can vary depending on how a website delivers or protects its media. How to use

Start playing a video, stream, or audio track.
Click Best Universal Volume Booster.
Pick your boost level.
Click Enable Boost.
If Firefox asks for additional site access, allow it so Best Universal Volume Booster can reach media players embedded from another website.
Turn on Auto-reapply if the site frequently replaces or reloads its media player.

Going all the way to 500% can make already-loud audio distort, so lower the boost if that happens. Site access Some websites display their actual video or audio player inside an embedded frame hosted on another domain. When necessary, Best Universal Volume Booster may ask for optional site access so it can reach and boost these cross-site embedded media players. This permission is requested when you enable the booster and is used to access compatible media players. Boosting itself only runs on tabs where you activate the extension. Best Universal Volume Booster does not use this access to collect browsing history or personal information. Privacy Best Universal Volume Booster does not collect, transmit, or sell personal data. The extension runs locally in Firefox. Your selected volume level and auto-reapply setting are stored locally in your browser. There are:

No analytics
No tracking
No external accounts
No advertising identifiers
No personal data collection

Compatibility Best Universal Volume Booster works by connecting to compatible browser media elements and processing their audio locally. Some websites use DRM, protected media, cross-origin media restrictions, closed Shadow DOM components, custom playback systems, or other browser restrictions that extensions cannot always access. Because of this, compatibility cannot be guaranteed on literally every website.