JWT Decoder
Decode and inspect JSON Web Tokens (JWT) by separating and displaying the Header, Payload, and Signature components with beautifully formatted JSON output and human-readable timestamp parsing for expiration (exp), issued-at (iat), and not-before (nbf) claims. JWTs are the standard authentication mechanism for modern web applications, mobile APIs, and microservice architectures — and being able to quickly inspect their contents is essential for debugging authentication flows, verifying token claims, checking expiration status, and understanding token structure. Our decoder processes the token entirely client-side in your browser, which is critically important because JWTs often contain sensitive user identifiers, roles, permissions, and session data that should never be transmitted to third-party decoding services. Paste any JWT string and instantly see the decoded algorithm, issuer, audience, custom claims, and formatted expiration dates.
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How to use JWT Decoder
- 1 Paste your JWT string (e.g. eyJhbGciOi...).
- 2 View parsed Header and Payload sections instantly.
- 3 Check token expiration (exp), issued at (iat), and custom claims.
Key Features of JWT Decoder
Zero Server Transmission
Tokens are parsed locally in memory; never sent across any network.
Claim Timestamp Inspector
Automatically converts "exp", "iat", and "nbf" claims into readable dates.
When to Use JWT Decoder
Authentication Debugging
Decode JWT access and refresh tokens to inspect claims, verify expiration times, and debug authentication flows during development.
API Security Auditing
Inspect JWT tokens from third-party APIs to verify what data is shared and ensure no sensitive information is exposed.
OAuth Flow Testing
Decode ID tokens from OAuth/OIDC providers (Google, GitHub, Auth0) to verify user identity claims and scope permissions.
Frequently Asked Questions
Does this tool verify the JWT signature?
No. This tool decodes token payload data for inspection. It does not verify cryptographic signatures.
Is it safe to paste production tokens?
While decoding is 100% client-side, we always recommend caution when handling sensitive production tokens.
What are the common JWT claims like exp, iat, and sub?
"exp" is the expiration timestamp, "iat" is the issued-at timestamp, "sub" is the subject (usually a user ID), "iss" is the token issuer, and "aud" is the intended audience. This tool automatically converts timestamp claims to human-readable dates.
Does the decoder verify JWT signatures?
The decoder displays header, payload, and signature components. Signature verification requires the secret/public key, not needed for inspection.
Is it safe to paste JWTs into this tool?
Our JWT Decoder runs entirely in your browser and the token is never sent to any server. However, avoid pasting production tokens with real user data.
Pro Tips & Best Practices
Security Best Practice
JWT payloads can contain sensitive user data. Decode tokens only in secure development environments, never in shared or production logs.
Check Expiration Claims
Always verify "exp" (expiration) and "iat" (issued at) claims. Expired tokens should trigger a refresh flow, not a hard failure.
Inspect Algorithm Header
Check the "alg" field in the header. Be wary of "none" algorithm (a known vulnerability) and ensure it matches server configuration.