Can You Install Firefox Extensions on Tor Browser?

While you can technically install standard Firefox extensions on the Tor Browser because it is built on Mozilla Firefox Extended Support Release (ESR), doing so is strongly discouraged. Adding third-party extensions undermines the core purpose of the Tor Browser by compromising your anonymity, creating unique tracking fingerprints, and potentially leaking your true IP address.

The Technical Reality

Because the Tor Browser shares its underlying codebase with Firefox, the browser technically allows you to visit the Firefox Add-ons store and install extensions just as you would on standard Firefox. However, the Tor Project intentionally restricts and warns against this behavior during installation.

Why You Should Avoid Installing Extensions

Browser Fingerprinting: Tor Browser is designed to make all users look identical to web servers. When you install an extra extension, you modify your browser’s unique configuration (its “fingerprint”). This allows websites and tracking networks to distinguish your session from millions of other Tor users, effectively defeating your privacy.
IP and DNS Leaks: Standard Firefox add-ons are not tested or audited for use with the Tor network. A rogue or poorly coded extension can make direct HTTP/HTTPS requests that bypass the Tor proxy entirely, exposing your real IP address and location to third parties.
Invasive Permissions: Many extensions require broad permissions to read, modify, and transmit data from every webpage you visit. This can compromise sensitive accounts, decrypt secure traffic locally, and expose browsing habits.

Built-in Extensions

The Tor Browser comes pre-configured with essential, heavily audited privacy tools out of the box, such as NoScript. These native components are fine-tuned to work seamlessly with the Tor routing protocol without leaking identifiable data.

To maintain maximum anonymity and security, rely strictly on the default configuration and avoid adding any external Firefox extensions.