Tor: Should I install browser extensions in Tor Browser?

Short answer

Generally no. Tor Browser's included extensions and settings are tested together for privacy and security. Extra add-ons can change your browser fingerprint, make direct network requests, or break site isolation. The Tor Project strongly discourages installing them and does not support altered configurations. If a feature is essential, consider whether a separate browser session is more appropriate.

Sources

Tor Project: Browser extensions, Tor Project: Fingerprinting protections.