You can now enable First Party Dynamic Isolation in Firefox 77

The Nightly version of Mozilla Firefox 77 has Received a new custom mode option for enhanced tracking protection in privacy and security settings to allow users to enable the “dynamic first party isolation” feature in the Firefox browser, the feature can also be enabled by changing a preference value in about: config.

As of Firefox 53, Mozilla has hidden the first-party isolation feature behind a preference called privacy.first party.isolate, enabling it may cause certain sites to break. Over the years, Mozilla has built stronger privacy protections into Firefox in the form of improved tracking protection or content blocking modes. As of now, Firefox browser with standard ETP blocks tracking cookies, social media trackers, tracking content in private windows, fingerprints and crypto miners by default. Users who choose custom mode have the luxury of choosing which trackers and scripts to block.

So far, custom setting allows blocking these types of cookies in Firefox browser

  • Cross-site and social media trackers
  • Cookies from unvisited websites
  • All third-party cookies
  • All the cookies.

In addition to the above, the custom setting for Advanced Tracking Protection in Firefox Nightly provides another new option for cookies in the drop-down menu:

cross-site and social media trackers and isolate remaining cookies

New cross-site and social media trackers and option to isolate remaining cookies

Choosing this option may cause some websites to hang where you are unable to enter them. Dynamic FPI can also be enabled by changing the following preference in about:config to 5.


To test the feature, launch Firefox Nightly

1. Click on the menu, select Options

2. Privacy & Security > Custom,

3. Select “Cross-site and social media trackers and isolate remaining cookies”

You need to reload all tabs or you can restart your browser for the same.

reloading all tabs and isolating the cookie notice

When selecting the option, Firefox Nightly displays a warning at the bottom warning that “Blocking trackers and isolating cookies may affect the functionality of some websites”.

Related articles:

UBlock Origin v1.25 introduces first-party tracker blocking exclusively for Firefox [Not available in Chrome]

Firefox Version 69 Brings Improved Tracking Protection and Various Performance Improvements to Windows 10 and macOS

Firefox 70: Mozilla Updates Improved Tracking Protection Preferences

Firefox updates Protection Report to show real data about blocked trackers, adds Monitor and Lockwise sections

Mozilla Finds Tracking Protection in Firefox Decreases Page Load Time for Websites by 44%

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