What this tool does
JWT Debugger decodes JSON Web Token headers and payloads, then reports claim diagnostics and signature caveats.
← All Tools
🎫 JWT Debugger + Editor
Decode JSON Web Token headers and payloads, inspect issuer/audience/expiry claims, and keep signature caveats visible.
JWT debugging checks
Base64URL-decodes header and payload JSON, highlights issuer/audience/subject/expiry timing, flags alg=none, and reports that signature verification is not performed.
Why it is useful
It helps developers and agents troubleshoot auth claims, expiration times, issuers, audiences, and token structure without treating decoded text as verified trust.
How it works
The shared core splits header.payload.signature, Base64URL-decodes the first two segments, parses JSON, and derives readable claim timing diagnostics.
Best input
Use development tokens, redacted samples, or locally generated examples. Avoid production bearer tokens and customer claims.
Security tip
Decoding is not verification. Server-side verification must enforce algorithm, key, issuer, audience, expiry, and revocation rules.
Privacy note
Browser use is local; the API route submits the token to Utilito's serverless function for automation.
Important limitation
This tool does not verify signatures, contact JWKS endpoints, decrypt JWE tokens, or decide whether a server will accept the token.
Quick answers
Is a JWT encrypted?
Usually no. Most JWT payloads are only encoded and can be read by anyone with the token.
Can this prove a JWT is valid?
No. It decodes and diagnoses structure; validation requires the issuer's verification keys and policy checks.
Common Use Cases
Inspect auth claims during development
Paste a local or redacted token to check issuer, audience, scopes, and custom claims without sending it to a third-party service.
Check token expiration quickly
Decode exp, iat, and nbf values while debugging login sessions or refresh-token flows.
Attach safe auth context to bugs
Copy the JSON summary from a redacted token so teammates or agents can see claim diagnostics without a raw bearer token.