Firefox 74 comes with an enhanced Facebook Container Extension that lets users add custom sites so they can login with Facebook wherever they need
Tim Anderson / The Register :
Context & Ripple Effects
Mozilla launched the Facebook Container Extension in 2018 to wall off Facebook's ability to track Firefox users across other sites — but the strictness cut both ways, since anyone who needed a Facebook login on a third-party site had to break the container. Firefox 74 loosens that trade-off by letting users add custom sites to the container, so login flows work without dissolving the isolation.
The update slots into a longer arc of Mozilla shipping privacy features directly into the browser rather than leaving them to add-ons: two years later it followed up with URL-level stripping of Meta, HubSpot, and Marketo trackers, functionality Brave had offered first.
First-order effects
- Firefox users who rely on 'Log in with Facebook' buttons no longer have to choose between account access and cross-site tracking protection — custom sites can be added to the container instead.
- Facebook loses one of its remaining friction points for pulling logged-in activity data from non-Facebook pages within Firefox, since the container now accommodates those logins rather than being abandoned when they're needed.
Second-order effects
- Rival browser makers face raised expectations: Brave's earlier URL-tracker stripping showed the feature bar, and Mozilla matching it signals that anti-tracking is becoming table stakes rather than a differentiator.
- Ad-tech firms dependent on cross-site identity — with Meta the largest named target across both the container and the URL-stripping feature — see a growing share of the Firefox base hardened against their pixels and query parameters.
Third-order effects
- If the pattern holds, the browser becomes the primary enforcement layer for web privacy — with Mozilla iterating from site containers to parameter stripping — displacing both platform self-regulation and slower regulatory remedies as the place where tracking limits actually get set.
- Identity providers built on cross-site login and measurement face structural pressure to move toward first-party, on-domain authentication models as browsers systematically close the side channels.
The trend: Browser vendors are steadily absorbing anti-tracking from optional extensions into core product features, making the client — not the platform or the regulator — the default arbiter of who can follow users across the web.