Free Online JWT Decoder
JSON Web Tokens (JWTs) carry authentication and authorization claims between services, APIs, and single-page applications. When debugging login flows, inspecting token expiry, or verifying claim contents, you need to decode the header and payload without sending sensitive tokens to unknown servers. Our free JWT decoder parses tokens entirely in your browser.
Paste a JWT and instantly see the decoded header, payload, and signature section. Your token is never uploaded — all decoding happens locally with client-side JavaScript.
How to Use the JWT Decoder
Paste your JWT into the input field. The tool splits the token into its three Base64URL-encoded parts — header, payload, and signature — and decodes the JSON header and payload for readable inspection. Check the exp claim for expiry, iss for issuer, and sub for subject. The signature is displayed but not verified unless the tool supports verification with a secret or public key.
Why JWT Decoder Matters
JWTs are everywhere in modern auth: OAuth 2.0, OpenID Connect, API gateways, and microservices all rely on them. Misconfigured expiry, wrong issuer claims, or missing scopes cause production auth failures that are hard to trace without decoding the token. A local decoder lets developers debug safely without exposing bearer tokens to third-party services.
Who Uses a JWT Decoder?
- Backend developers debug API authentication and verify claim structure during integration.
- Frontend developers inspect tokens stored in localStorage or cookies after OAuth flows.
- DevOps and SRE teams troubleshoot service-to-service auth without sharing tokens externally.
- Security engineers audit token claims, expiry windows, and algorithm choices.
- QA testers validate login flows and session expiry behavior in staging environments.
Key Features
- Decode JWT header and payload to formatted JSON
- Display all three token segments (header, payload, signature)
- Client-side only — tokens never leave your browser
- Instant parsing with no server round trip
- Free with no sign-up required
Tips for Getting the Most From This Tool
Never paste production JWTs into untrusted online decoders. This tool processes tokens locally, but treat all tokens as secrets. Check the alg claim in the header — avoid none algorithm in production. Compare exp (expiry) against current Unix time to diagnose session timeout issues.
Frequently Asked Questions
Does this tool verify JWT signatures?
Decoding shows header and payload contents. Signature verification requires the secret or public key used to sign the token and may be supported separately.
Is it safe to paste my JWT here?
This tool decodes locally in your browser without uploading your token. Still, avoid pasting production tokens on any website when possible.
What claims should I look for?
Common claims include sub (subject), iss (issuer), aud (audience), exp (expiry), iat (issued at), and scope or roles for authorization.
Why is my token three dot-separated parts?
JWTs use the format header.payload.signature, each part Base64URL-encoded. The signature ensures integrity and authenticity.