Firebase: Firebase Hosting returning unexpected 431 errors on some POST requests to Firebase Functions rewrites
Affected components: Hosting
Timeline of updates
- service disruption
POST requests against Firebase Hosting Sites with rewrites to Firebase Fuctions can occasionally return unexpected 431 errors.
- resolved
The Firebase Hosting team is currently rolling out a fix. It should be available globally within a few hours.
Archive proof
Rewindex commits each version of an incident it captures to a daily checkpoint, chains it to the day before, and has the checkpoint timestamped by FreeTSA and DigiCert. That proves this record existed by then and has not been changed since, by anyone, Rewindex included.
How the archive is checked, and what it cannot prove.
First version captured
In the 2026-10-19 checkpoint, timestamped by FreeTSA and DigiCert on . Record hash
c729d70fd849ca33…
Impact, status and times are the vendor’s own, as last archived. View on status.firebase.google.com (opens in new tab).
Cite this
Status incident (vendor impact label: minor) posted by Firebase, started 2025-12-20 17:00 UTC, resolved after 17 d, 2 update(s).
- Title
- Firebase Hosting returning unexpected 431 errors on some POST requests to Firebase Functions rewrites
- Vendor
- Firebase
- Date
- URL
- https://rewindex.com/company/firebase/incidents/51yhjchdin3mc1542mkd
Firebase profileRecent Firebase incidentsAll outages on December 20, 2025Firebase in December 2025MarkdownJSON