JWT Decoder
Decode JWT tokens and inspect claims.
JSON Web Tokens carry signed claims between services, but their header and payload are Base64-encoded JSON, not encrypted. Utilitoo's JWT Decoder splits a token into its three parts, decodes the header and payload, and displays the claims in readable JSON so you can inspect expirations, roles, and issuer details.
Reach for this tool when debugging OAuth flows, verifying what scopes a token contains, or checking whether a session expired. Support engineers use it to decode customer tokens during incident response, and developers use it when integrating third-party identity providers like Auth0, Okta, or Firebase.
Important: decoding is not verification. This tool does not validate signatures or trust the token. Always verify signatures server-side in production. For deeper inspection, combine with our JSON Formatter to pretty-print decoded claims, or Base64 Encode/Decode for individual segments.
Your tokens never leave your browser on Utilitoo. We do not store, log, or transmit JWTs. Free, private, and built for developers, security engineers, and anyone troubleshooting authentication in distributed systems. Identity engineers reviewing token lifetimes, custom claims, and algorithm headers benefit from a decoder that works offline and respects data boundaries during security reviews. You can inspect tokens from mobile apps, server logs, and browser devtools network tabs without leaving the page you are already working in.
JWT Decoder converts between representations without a local toolchain install. Decode JWT tokens and inspect claims. Round-trip a small fixture when possible so you catch encoding edge cases before batch work.
Common use cases
- Debugging a failing API or config by running JWT Decoder on a staging sample before changing production.
- Preparing jwt decoder output to paste into a pull request, incident ticket, or team chat.
- Checking third-party jwt decoder payloads before wiring them into application code.
- Teaching jwt decoder concepts in a workshop without installing CLI tooling on every laptop.
- Comparing JWT Decoder output with a teammate during pair review when formats disagree.
Tips & common mistakes
JWT Decoder runs in your browser on Utilitoo - paste staging payloads without a server upload. Start with a small sample to confirm format, then process the full input. If output looks wrong, check truncation, encoding, and mixed line endings from terminals or log viewers. Pin the tab during active debugging and chain Related Tools instead of returning to the homepage. Remember that decoding a JWT does not verify its signature - never trust claims from an unverified token in security decisions.
Common errors
- Invalid padding - Base64 strings need correct = padding; mid-string whitespace can break decoding.
- Wrong alphabet - URL-safe Base64 differs from standard; select the matching mode.
How to use
- Paste JWT token.
- View decoded header and payload.
Frequently Asked Questions
How do I decode a JWT token online?▼
Paste the full JWT into Utilitoo. The tool splits header, payload, and signature, then decodes the JSON parts automatically.
Can I decode a JWT without the secret key?▼
Yes. JWT headers and payloads are Base64-encoded, not encrypted. Anyone can read them. Only the signature requires the secret to verify.
Does this tool verify JWT signatures?▼
No. Utilitoo decodes and displays claims for inspection only. Always verify signatures in your backend before trusting a token.
Is it safe to paste production JWTs into an online decoder?▼
On Utilitoo, yes. Decoding runs locally in your browser. Tokens are not uploaded or stored on any server.
What JWT claims should I check first?▼
Start with exp (expiration), iss (issuer), aud (audience), and sub (subject). These tell you whether the token is still valid and intended for your app.
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