Blue Blocker is a browser extension that parses incoming API responses between the user's browser and the Twitter services to detect Twitter Blue users and subsequently block them via the same Twitter API.
To facilitate this, Blue Blocker stores the most recently used cookies and headers sent by the Twitter web client. Blue Blocker uses these cookies and headers to send block requests to the Twitter API and for no other purposes. Blue Blocker does not record, track, sell, or otherwise use your data. Blue Blocker does not send any requests to any service containing any user data outside of block and mute requests to the Twitter API.