https://github.com/omarroth/invidious

Invidious is an alternative front-end to YouTube https://invidio.us

Audio-only mode (and no need to keep window open on mobile)
Free software (AGPLv3 licensed)
No ads
No need to create a Google account to save subscriptions
Lightweight (homepage is ~4 KB compressed)
Tools for managing subscriptions:
Only show unseen videos
Only show latest (or latest unseen) video from each channel
Delivers notifications from all subscribed channels
Automatically redirect homepage to feed
Import subscriptions from YouTube
Dark mode
Embed support
Set default player options (speed, quality, autoplay, loop)
Does not require JS to play videos
Support for Reddit comments in place of YT comments
Import/Export subscriptions, watch history, preferences
Does not use any of the official YouTube APIs
Developer API