Firebase Custom Claims Byte Limitation Requires Parallel Systems

6/10 Medium

Firebase Authentication's custom claims are limited to 1000 bytes, forcing developers to build parallel authorization systems in Firestore and essentially reimplement what should be infrastructure-level functionality.

Firebase AuthenticationFirestore
Category
compatibility
Workaround
hack
Stage
build
Freshness
persistent
Scope
framework
Upstream
wontfix
Recurring
Yes
Maintainer
active

Sources

Collection History

Query: “What are the most common pain points with Clerk for developers in 2025?”4/7/2026

Firebase Authentication famously struggles here—custom claims limited to 1000 bytes forces developers to build parallel authorization systems in Firestore, essentially reimplementing what should be infrastructure.

Created: 4/7/2026Updated: 4/7/2026