Open-source extensions let developers and security researchers inspect the code instead of trusting a vendor's word. That matters most for extensions with deep access, like ad blockers reading every page and password managers holding your logins. The picks below all publish their source code publicly.
Open-source ad blocking and privacy
uBlock Origin Lite is open source and built on Manifest V3, so its ad and tracker-blocking rules are publicly auditable. Dark Reader is also open source, applying a dark theme to any website by generating styles on the fly rather than sending your browsing to a remote service.
Open-source password management
Bitwarden publishes its full codebase, including its browser extension, mobile apps and server. It offers a free plan alongside paid tiers for teams and extra features. Being open source lets independent researchers verify how it encrypts and stores your passwords.
Open-source developer and reading tools
JSON Formatter and Video Speed Controller are both open source and free, doing one focused job each. React Developer Tools is maintained openly by the React team itself. Read Aloud, a free text-to-speech tool, also publishes its source for anyone to review.