About JWT Decoder

About This Tool

JWT Decoder is a free online tool for developers who work with JSON Web Tokens. Decode, inspect, and verify JWT tokens instantly — with expiration time visualization in any timezone, security warnings for common issues, and explanations for all standard claims. All processing happens entirely in your browser.

Key Features

• Instant JWT decoding with syntax-highlighted Header and Payload
• Expiration time visualization with timezone support and countdown
• Security warnings: alg:none detection, missing expiration, sensitive data in claims
• Standard claim explanations (iss, sub, aud, exp, nbf, iat, jti)
• HS256 signature verification using Web Crypto API
• Integration with JSON Formatter for detailed payload inspection
• 100% free, runs entirely in your browser — no data sent to any server

Who Is This For?

This tool is designed for backend developers debugging API authentication, frontend developers inspecting tokens in browser storage, security engineers auditing JWT configurations, and anyone who needs to quickly understand the contents of a JWT token.

Privacy

Your JWT tokens are processed locally in your browser using JavaScript. Nothing is sent to any server. This tool is safe to use with production tokens, access tokens, and sensitive credentials.