Looks like they stopped doing it

https://localmess.github.io

> UPDATE: As of June 3rd 7:45 CEST, Meta/Facebook Pixel script is no longer sending any packets or requests to localhost. The code responsible for sending the _fbp cookie has been almost completely removed. Yandex has also stopped the practice we describe below.

Chrome and Firefox have deployed / are deploying local-network-access which prompts the user when apps try this.

> Meta must face a lawsuit alleging that it secretly tracked Android users' browsing activity on mobile websites that embedded Meta's analytics pixel, and linked that activity to users' identities, a federal judge ruled Monday.

> The decision, issued by U.S. District Court Judge Rita Lin in San Francisco, grew out of a class-action complaint initially brought last June by California resident Devin Rose (and later joined by other Android users).

> Rose alleged that between September 2024 and June 2025, Meta exploited Android's localhost -- a feature that allows software developers to test applications -- to connect users’ mobile web browsing to their Facebook and Instagram profiles.

May 12, 2026

i would love to have a software engineer's union, not so much to get better working conditions but to be able to say stuff like "i can't implement that unethical feature, it's against union rules and i'd lose my membership".