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JWT Decoder

Decode JWT tokens · Header / Payload / Signature

JWT TokenJWT
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HEADERJSON
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PAYLOADJSON
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SIGNATURE
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Overview: JWT Decoder is a debugging tool built to parse JSON Web Tokens. It splits the compact three-segment string into readable Header, Payload and Signature sections, and intelligently detects the expiration time (exp) in the payload, helping developers investigate authentication, single sign-on and API token issues.

How to use: Step 1 — paste a complete JWT (in the form xxxxx.yyyyy.zzzzz) into the input field, or click "Sample" to load a test token. Step 2 — the tool automatically Base64URL-decodes the Header and Payload and formats them as readable JSON. Step 3 — if the Payload contains an exp claim, the tool compares it with the current time and shows a prominent warning when the token has expired. Step 4 — the Signature is shown as raw Base64URL because verifying a signature requires the secret and must be done server-side. Step 5 — copy the decoded Header or Payload to help debugging.

Typical scenarios: Debug OAuth 2.0 and OIDC flows by inspecting claims in access_token or id_token; front-end developers pull tokens from Cookies or LocalStorage to check identity fields (sub, role, iat, exp); verify JWTs issued through microservice gateways such as Kong or APISIX; debug cross-system token propagation while onboarding an SSO integration.

Technical notes: The tool only parses JWT structure; it does not verify HMAC, RSA or ECDSA signatures (which need the signing key or public key and must be done on the server). Base64URL uses -/_ instead of standard Base64’s +//, and the tool auto-pads. A JWT has three segments separated by .; other segment counts trigger an error. exp, iat and nbf are Unix timestamps (seconds) that are compared to the current time.

Privacy: Parsing runs entirely in your browser and no token content is uploaded. Note, however, that a production token is effectively a user credential — avoid leaking it on public devices or in public chat tools.

Frequently Asked Questions

How do I use JWT Decoder?
Step 2 — the tool automatically Base64URL-decodes the Header and Payload and formats them as readable JSON. Step 3 — if the Payload contains an exp claim, the tool compares it with the current time and shows a prominent warning when the token has expired.
What can JWT Decoder do?
Typical scenarios: Debug OAuth 2.0 and OIDC flows by inspecting claims in access_token or id_token ; front-end developers pull tokens from Cookies or LocalStorage to check identity fields ( sub , role , iat , exp ); verify JWTs issued…
Is my data private when I use JWT Decoder?
Note, however, that a production token is effectively a user credential — avoid leaking it on public devices or in public chat tools. Note, however, that a production token is effectively a user credential — avoid leaking it on public devices or in public chat tools.
What technical details should I know about JWT Decoder?
Base64URL uses - / _ instead of standard Base64’s + / / , and the tool auto-pads. A JWT has three segments separated by . ; other segment counts trigger an error. exp , iat and nbf are Unix timestamps (seconds) that are compared to the current time.