JWT Decoder
LiveDecode and inspect JSON Web Tokens to view header, payload, and signature.
Understanding JSON Web Tokens (JWT)
JSON Web Tokens (JWT) are compact, URL-safe tokens used for stateless authentication and information exchange. A JWT consists of three Base64url-encoded parts separated by dots: a header specifying the signing algorithm (HS256, RS256, ES256), a payload containing claims like user ID, roles, issuer, and expiration time, and a signature that verifies the token has not been tampered with. JWTs are foundational to modern authentication — OAuth 2.0, OpenID Connect, and API authentication systems use them to carry verified identity information between services.
Decode JWT tokens to inspect header algorithm, payload claims, expiration dates, and signature details without verification.
The Devkitr JWT Decoder splits any JWT into its three components and displays the decoded header and payload as formatted JSON. Paste a token from an Authorization header, cookie, or authentication response to immediately see all embedded claims — subject, issuer, audience, expiration, issued-at time, and custom claims — without writing any code or using JWT libraries.
In a typical development workflow, JWT Decoder becomes valuable whenever you need to decode and inspect json web tokens to view header, payload, and signature. Whether you are working on a personal side project, maintaining production applications for a company, or collaborating with a distributed team across time zones, having a reliable browser-based processing tool eliminates the need to install desktop software, write one-off scripts, or send data to third-party services that may log or retain your information. Since JWT Decoder processes everything locally on your device, your data stays private and your workflow stays uninterrupted — open a browser tab, paste your input, get your result.
Key Features
Three-Part Breakdown
Separates the JWT into header, payload, and signature sections, displaying each decoded component with syntax-highlighted JSON formatting.
Claim Interpretation
Highlights standard claims (sub, iss, aud, exp, iat, nbf) with human-readable labels and converts Unix timestamps to readable dates.
Expiration Status Check
Compares the exp claim against the current time and clearly indicates whether the token is currently valid, expired, or not yet valid (nbf).
Algorithm Identification
Displays the signing algorithm from the header (HS256, RS256, ES256, PS256) so you can verify it matches your expected security configuration.
How to Use JWT Decoder
Obtain a JWT
Copy a JWT from a login response, Authorization header, browser cookie, or developer tools Network panel.
Paste the Token
Enter the complete JWT (all three dot-separated parts) into the decoder input field.
Read the Decoded Claims
Review the header for algorithm info and the payload for user identity, permissions, expiration, and custom claims.
Check Token Status
Verify the expiration time, issuer, and audience claims match your application's expected values for the current authentication context.
Use Cases
Debugging Authentication Failures
Decode a rejected JWT to check whether it is expired, issued for the wrong audience, or missing required claims that the server validates.
Inspecting OAuth2 Access Tokens
Decode access tokens from OAuth2 providers (Auth0, Okta, Firebase) to see granted scopes, user metadata, and token lifetime.
Verifying Role-Based Access Control
Inspect the roles or permissions claims in a JWT to confirm users are assigned the correct access levels for your application.
Auditing Third-Party Tokens
Decode tokens from external identity providers to understand what user information is shared and verify data minimization compliance.
Pro Tips
Check the exp claim timezone — JWT timestamps are always in Unix epoch seconds (UTC). Convert to your local timezone for meaningful comparison.
Look at the "alg" header to verify the signing algorithm. Tokens using "none" or unexpected algorithms may indicate a security vulnerability.
Use the iat (issued at) and exp claims together to calculate token lifetime — this helps debug refresh token flows and session duration issues.
Decode JWTs in the browser only for inspection. Never paste production tokens with real user data into online decoders that send data to a server.
Common Pitfalls
Trusting JWT payload contents without verifying the signature
Fix: Anyone can create a JWT with any payload. Always verify the signature server-side using the correct key before trusting claims for authorization.
Storing JWTs in localStorage where they are accessible to XSS attacks
Fix: Store JWTs in httpOnly cookies to prevent JavaScript access. If localStorage is required, implement robust XSS prevention and keep token lifetimes short.
Using JWTs for session management without a revocation strategy
Fix: JWTs cannot be invalidated before expiry by default. Implement token blacklisting, short expiration with refresh tokens, or use opaque session tokens for revocable sessions.
Frequently Asked Questions
QDoes this tool verify JWT signatures?
This tool decodes and displays the token contents but does not verify the signature. It is designed for inspection and debugging.
QIs it safe to paste my JWT here?
Yes. The decoding happens entirely in your browser. Your token is never sent to any server.
QWhat JWT claims are displayed?
All standard claims (iss, sub, aud, exp, nbf, iat, jti) and any custom claims in the payload are displayed.
QCan I see if a token is expired?
Yes. The tool checks the exp (expiration) claim and shows whether the token is still valid or has expired.
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