What is First-Party Isolation?
A browser feature that separates website data (cookies, cache, storage) so that one website cannot access data set by another.
First-Party Isolation (FPI) prevents cross-site tracking by ensuring that data from one website is invisible to another.
How It Works
- Each website gets its own isolated storage container
- Cookies set by site A are invisible when you visit site B
- Third-party resources (like a Facebook Like button) get a separate container per first-party site
- Prevents cookies from being used to track you across the web
Browser Support
- Firefox: Available via
privacy.firstparty.isolateor Total Cookie Protection (enabled by default) - Tor Browser: Enabled by default and more aggressive than Firefox
- Brave: Similar isolation through partitioned storage
Trade-offs
- Some legitimate cross-site functionality may break (SSO login, embedded content)
- Websites that embed third-party login buttons may need you to re-authenticate
- The privacy benefit generally outweighs the inconvenience
Related Terms
Browser Fingerprinting
A tracking technique that collects information about your browser, device, and settings to create a unique identifier. Unlike cookies, fingerprints are nearly impossible to delete and can track you across websites without your knowledge or consent.
Cookie
A small piece of data stored in your web browser by websites you visit. While cookies enable useful features like staying logged in, they're also used extensively for tracking your browsing activity across the web for advertising and analytics purposes.
Third-Party Tracking
The practice of monitoring user behavior across multiple websites using embedded scripts, pixels, cookies, and fingerprinting techniques.
Have more questions?
Use our guided flow to get the right next privacy step for First-Party Isolation.
Open Guided Flow