JWT Decoder – Free Online Tool
Free online JWT decoder and parser. Decode JSON Web Tokens instantly, inspect headers, payloads, and claims with color-coded visualization, token timeline, security warnings, and claim-level copy — all 100% client-side.
What Is a JSON Web Token (JWT)?
A JSON Web Token (JWT) is a compact, URL-safe standard (RFC 7519) for securely transmitting claims between two parties. Every JWT has three parts separated by dots: a Header (algorithm and token type), a Payload (user claims and metadata), and a Signature (cryptographic verification). JWTs are the backbone of modern authentication in OAuth 2.0, OpenID Connect, API authorization, and single sign-on systems.
How Does Our JWT Decoder Work?
Our decoder splits your JWT into its three Base64Url-encoded parts, decodes each segment, and presents the resulting JSON with syntax highlighting and color coding. It automatically detects timestamp claims (exp, iat, nbf) and converts them to human-readable dates with relative time labels like 'expired 2 hours ago' or 'valid for 23 minutes'. Everything runs in your browser using client-side JavaScript — no server requests, no data transmission.
Why Choose Our JWT Decoder Over jwt.io?
While jwt.io is the industry standard, our decoder offers unique features: a visual token expiration timeline showing iat, nbf, and exp relative to now; security warnings for dangerous patterns like 'alg: none' or missing expiration claims; claim-level copy buttons for any individual value; token size analysis to catch oversized tokens that break HTTP header limits; decode history persisted in local storage; and standard claim descriptions so you understand what each field means.
Who Needs a JWT Decoder?
JWT decoders are essential for backend developers debugging authentication flows, frontend engineers inspecting access tokens from OAuth providers, DevOps engineers troubleshooting SSO and API gateway configurations, security auditors reviewing token claims and expiration policies, QA testers verifying token payloads in staging environments, and students learning about modern web authentication standards like OAuth 2.0 and OpenID Connect.
How to Use JWT Decoder
- 1
Paste your JWT into the input field — you can paste the raw token or a full URL containing a JWT parameter, and our tool will auto-extract it
- 2
Instantly view the color-coded Header (red), Payload (purple), and Signature (blue) with pretty-printed JSON
- 3
Inspect individual claims with descriptions, copy any value with one click, check the expiration timeline, and review security warnings for best practices
Frequently Asked Questions
Everything you need to know about the JWT Decoder.
Is it safe to paste my production JWT here?
Yes. Our JWT decoder runs entirely in your browser using client-side JavaScript. Your token is never transmitted to any server, stored in any database, or logged in any analytics. It is completely safe for production tokens, access tokens, refresh tokens, and ID tokens containing sensitive user data.
Does this tool verify JWT signatures?
This tool performs structural decoding and inspection only. It does not verify cryptographic signatures because doing so requires the secret key or public key used by the issuing server. For security, secret keys should never be pasted into any online tool. We clearly display the algorithm (HS256, RS256, etc.) from the header so you know what verification method is expected.
How do I read the exp, iat, and nbf timestamps?
JWTs store timestamps as Unix epoch seconds (seconds since January 1, 1970). Our tool automatically detects exp (Expiration Time), iat (Issued At), and nbf (Not Before) claims and converts them to human-readable dates in your local timezone. We also show relative time labels like 'expired 3 hours ago' or 'valid for 45 minutes' and display a visual timeline bar.
Why does my token not decode properly?
A valid JWT must have exactly three parts separated by periods (dots). The first two parts must be valid Base64Url-encoded JSON objects. Common issues include: truncated tokens (copy the full string), extra whitespace or newlines, tokens with only 2 parts (unsigned JWTs), and corrupted Base64 encoding from incorrect URL encoding.
What JWT claims does the decoder recognize?
Our decoder recognizes all standard IANA JWT claims: iss (Issuer), sub (Subject), aud (Audience), exp (Expiration), nbf (Not Before), iat (Issued At), jti (JWT ID), as well as common custom claims like name, email, roles, scope, permissions, and provider-specific claims from Auth0, Firebase, AWS Cognito, and Azure AD.
Can I decode JWTs from a URL parameter?
Yes! If you paste a full URL containing a JWT in a query parameter (like ?token=eyJhbG... or ?id_token=eyJhbG...), our tool automatically extracts and decodes the JWT. This is especially useful when debugging OAuth callback URLs, SSO redirects, and API responses.