JWT debugger
Decode, inspect, verify, and generate JSON Web Tokens locally in your browser with HMAC-SHA256.
JWT debugger
100% Client-Side In-Browser • HMAC (HS256, HS384, HS512)
How to Use JWT debugger
Paste or Enter Token
Paste an encoded JWT into the token area or edit Header and Payload JSON directly.
Inspect Claims
View decoded claims including expiration (exp), issued at (iat), not before (nbf) status.
Verify or Sign
Enter your secret key to verify the HMAC-SHA256 signature or generate a new signed token.
Key Benefits
- 100% Private: Confidential tokens and secret keys never leave your browser
- Instant syntax validation with color-coded token segments
- Built-in expiration countdown and claim inspector
- Sign and verify HS256 tokens using native Web Crypto API
Browser & Hardware Notes
- Asymmetric algorithms (RS256, ES256) signature verification is not yet supported in this version.
Frequently Asked Questions about JWT debugger
How JWT debugger Operates Privately on Your Device
Unlike traditional cloud services that transmit your confidential files across the open internet to remote servers, SafeWebUtil operates on a strict zero-upload client-side architecture. Every transformation performed by JWT debugger executes exclusively within your browser's secure memory sandbox.
Native Web Crypto API (SubtleCrypto)
All cryptographic hashing, signing, and encryption routines strictly execute through browser-native Constant-Time primitives, immune to timing side-channel attacks.
Authenticated Military-Grade Ciphers
Utilizes AES-256-GCM authenticated encryption and PBKDF2 with high iteration counts to ensure data confidentiality and cryptographic tamper resistance.
Zero Ingestion & Ephemeral Memory
Plaintext passwords, JWT tokens, and symmetric keys reside exclusively in temporary JavaScript memory and are zeroized as soon as the tab is closed.
Engineering Insights & Performance Best Practices for JWT debugger
Cryptographic algorithms execute via constant-time Web Crypto primitives. Confidential JWT tokens, private passwords, and symmetric encryption keys never leave your machine.
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