Intent to ship: Enable State Partitioning in Private Browsing Mode

[Tim Huang]

# Summary

We would like to enable State Partitioning[1] in private browsing windows.
State Partitioning has been enabled in Strict Mode since Firefox 86[2] to
provide better protection against trackers. Now, we want to expand the
protection to the private browsing mode so that more users could benefit
from State Partitioning.

We use the cookie behavior to decide if State Partitioning is enabled in
Firefox. We used to have one single pref to control the cookie behavior for
both regular and private browsing mode. To enable State Partitioning in
private mode, we will introduce a new pref
“network.cookie.cookieBehavior.pbmode” to control the cookie behavior in
private browsing mode. By doing this, we can control the cookie behavior
individually and enable State Partitioning in private browsing mode without
affecting regular mode.

Our current plan is to enable State Partitioning in private mode in Firefox
89. And it is expected to ride the trains.

Previous intent to prototype is here:
https://groups.google.com/g/mozilla.dev.platform/c/f2_hLdfsbq4/m/ZhuWE4ZAAgAJ?pli=1


# Bug

https://bugzilla.mozilla.org/show_bug.cgi?id=1698810


# Standard

https://github.com/privacycg/storage-partitioning/

Note that this spec is still a work in progress.


# Platform coverage

All


# Preference

network.cookie.cookieBehavior.pbmode


# DevTools Bug

None


# Other browsers

Chrome: Chrome blocks third-party cookies in incognito mode.

Safari: Safari blocks all third-party cookies by default.


Thanks,

Tim


[1]: https://hacks.mozilla.org/2021/02/introducing-state-partitioning/

[2]: https://blog.mozilla.org/security/2021/02/23/total-cookie-protection/