JWT Builder & Signer
Build and sign JSON Web Tokens (JWTs) directly in your browser. HS256 / HS384 / HS512 (HMAC) signing via the native Web Crypto API. Color-highlighted output. Secret never leaves your browser.
What powers the JWT Builder
HS256, HS384, HS512 signing via browser SubtleCrypto
JSON payload editor
Color-highlighted output (header / payload / signature)
Pair with JWT Decoder for round-trip testing
secret never sent over network
Why the JWT Builder is different
Browser-native
The JWT Builder runs entirely in your browser. Input is processed locally — never uploaded, never logged, never cached anywhere outside your device.
No artificial limits
No daily quotas, no character ceilings, no "upgrade for more" walls. Every feature is the complete feature — the same on the first use as the thousandth.
Production-grade quality
Built to the same engineering bar as paid SaaS tools — accurate algorithms, audited logic, responsive design and accessibility-tested interactions.
Common use contexts
- Backend dev — testing JWT-validated endpoints with custom claims
- Frontend dev — generating mock tokens for local testing
- Learning JWT structure and signature math
- Debugging auth issues where you need to forge a token with specific claims
Private and secure
Zero upload
All processing happens in your browser. Input is never transmitted, logged or cached.
Works offline
Once the page loads, the tool runs without an internet connection. No network calls happen during use.
No tracking
No accounts, no cookies for tool state. Only aggregate analytics count visits at the page level.