JWT Decoder

JSON Web Tokens (JWTs) are the standard authentication mechanism in modern web applications, mobile APIs, and microservices. A JWT encodes user identity, roles, permissions, and expiry time in a self-contained token that is passed with every API request. A JWT consists of three Base64url-encoded sections separated by dots: the header (algorithm and token type), the payload (claims), and the signature. When debugging authentication failures, checking token expiry, or verifying what permissions a token grants, developers need to read the decoded contents. This JWT decoder splits any token into its three parts and shows the decoded JSON header and payload in a clean, human-readable format, along with the expiry timestamp converted to your local time for easy comparison. A common scenario is a frontend developer receiving a 401 Unauthorized response from a REST API who pastes the bearer token from the Authorization header to check whether the "exp" claim has already elapsed, instantly revealing that the token expired hours ago. Similarly, a backend engineer integrating with a third-party OAuth provider can verify that the "scope" or "roles" claim inside an access token contains exactly the right permissions before writing additional middleware or access-control logic. QA engineers testing staging environments also rely on this tool to pull a token directly from a browser's Application tab in DevTools and confirm that the "sub" subject and "email" fields match the test account that was just signed in. Backend and frontend developers, DevOps engineers troubleshooting Kubernetes service-to-service authentication, and security professionals auditing OAuth token payloads all benefit from fast, script-free visibility into token contents. Since JWTs frequently carry sensitive identity data such as email addresses, internal user IDs, and privilege levels, privacy is paramount — this tool runs entirely in your browser and never transmits your token data to any external server.