JWT Debugger — Decode & Inspect Offline (No Upload)
Create signed JWTs with HS256/HS384/HS512 or decode tokens side by side. All cryptography runs in your browser; nothing is sent to a server.
Frequently asked questions
No. Signing and decoding use Web Crypto locally. Nothing is sent to LocalTools servers for processing.
The debugger shows segments; signature verification against trusted keys is a separate step your backend should perform.
Related guides
- Reading a JWT without trusting the serverHow JWT structure, Base64URL encoding, and signatures work — and why decoding locally beats pasting tokens into random websites.
- Generating test JWT tokens locallyHow to create HMAC-signed JWTs for API mocks with iat and exp claims — and why signing should stay in your browser or CI, not a random website.