This JWT decoder is designed for web and mobile developers, backend engineers, DevOps professionals, and security researchers who need to quickly inspect API authentication token contents. A JWT (JSON Web Token, RFC 7519) is a compact string of three Base64Url-encoded sections—Header, Payload, and Signature—separated by dots. Paste any token to instantly view the Header's algorithm (alg: HS256, RS256, etc.) and type (typ), and see the Payload's standard claims (iss, sub, aud, exp, iat, nbf) and any custom claims rendered as a syntax-highlighted JSON tree. Expiration timestamps (exp) are converted from Unix epoch to your local timezone with a live countdown showing remaining validity. Signature verification requires the server's secret key and is deliberately not performed in this client-side tool. Remember: JWT payloads are encoded, not encrypted—anyone can decode them, so never place passwords, national IDs, credit card numbers, or other sensitive data inside a JWT payload. All processing happens entirely in your browser; your tokens are never transmitted anywhere.