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JSON Web Tokens (JWT) are opaque to humans but contain critical authentication and authorization data. Our decoder instantly parses JWTs into readable JSON, revealing header, payload, and claims without requiring secret keys, making API debugging and token inspection effortless.
🔍 Instant decoding - Parse JWT structure in real-time
đź“Š Three-part display - Header, payload, and signature separately shown
⏰ Expiration checking - Automatically detect expired tokens
🎨 Syntax highlighting - Color-coded JSON for easy reading
đź”’ Privacy-first - All decoding happens in your browser
đź“‹ Quick copy - Copy decoded JSON with one click
Understanding JWT Structure
JWTs have three parts: Header (algorithm), Payload (claims), Signature (verification). Our decoder separates these parts. Remember: decoding doesn't validate signature—that requires the secret key server-side.
Check Token Expiration
Look for 'exp' claim in payload. It's a Unix timestamp. If exp is past current time, token is expired. Expired tokens cause 401 Unauthorized errors. Use our epoch converter to verify expiration dates.
Inspect Claims for Debugging
Decode JWTs when debugging permission issues. Check 'sub' (user ID), 'roles', 'permissions', and custom claims. Mismatched claims explain why users can't access certain resources.
Never Expose JWTs
While decoding is safe (it's not encryption), JWTs grant access to your accounts. Never share actual tokens in public forums, screenshots, or logs. Use example tokens for demonstration purposes only.
Validate in Production
This tool decodes tokens but doesn't verify signatures. Production applications must validate JWT signatures using the secret key to prevent token tampering and ensure authenticity. Decoding alone isn't security.
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