JWT (JSON Web Token) Decoder Online Free
Decode and inspect JSON Web Tokens (JWT) directly inside your web browser. Inspect signing algorithms, examine payload claims, check issued-at timestamps, and verify token expiration dates with real-time countdown alerts.
JWT (JSON Web Token) Decoder In-Browser Workspace
Input data or select files to begin. 100% private, client-side execution with zero server transmission.
How to Use JWT (JSON Web Token) Decoder
- Step 1: Paste your encoded JSON Web Token (the three dot-separated strings starting with `ey...`) into the input area.
- Step 2: The decoder automatically splits and parses the Header, Payload, and Signature segments.
- Step 3: Inspect the color-coded decoded JSON panels for claims such as user IDs, email addresses, and roles.
- Step 4: Check the status banner to see whether the token is currently active or expired.
- Step 5: Click 'Copy JSON' to copy the structured claims directly into your development clipboard.
About JWT (JSON Web Token) Decoder
JSON Web Tokens (RFC 7519) are the foundational identity and authorization format utilized in OAuth 2.0, OpenID Connect, Supabase, Firebase, and enterprise single sign-on (SSO) systems. A JWT consists of three Base64URL-encoded segments separated by dots: a Header specifying the cryptographic signing algorithm (such as HS256 or RS256), a Payload containing JSON claims (like subject `sub`, expiration `exp`, and issued-at `iat`), and a cryptographic Signature validating authenticity. Because the Header and Payload segments are merely Base64URL-encoded (not encrypted), developers can decode and inspect the data claims client-side without providing secret private keys. Our JWT Decoder executes 100% in local browser memory, ensuring your production authentication tokens and user emails are never logged or exposed to remote servers.
Frequently Asked Questions
Does decoding a JWT require my private secret key?
No. The Header and Payload parts of a JWT are encoded in standard Base64URL and can be decoded by anyone. The private secret key is only required to verify or sign the token.
Can this tool modify and re-sign a JWT?
To re-sign a modified token, you would need the secret signing key. Since this tool operates with strict browser privacy and does not collect keys, it focuses on decoding and debugging.
What does the 'exp' claim represent?
The 'exp' claim is a Unix epoch timestamp (seconds since January 1, 1970) indicating the exact moment when the token expires and should no longer be accepted by APIs.
Are my authentication tokens transmitted to any remote server?
Never. All parsing and Base64URL decoding execute 100% locally in your browser sandbox. Your tokens remain completely confidential.