Advanced JWT Debugger
Decode tokens, verify HS256 signatures, and inspect payload schemas accurately.
Encoded Token
Verify Signature
UnverifiedHeader ALGORITHM & TTYP
Payload CLAIMS
About Advanced Online JWT Decoder & Verifier
A powerful developer tool to decode, inspect, and mathematically verify JSON Web Tokens (JWT) locally. Parse expiration dates, calculate mathematical signatures via HS256, and ensure your identity tokens are secure.
How to Use
- 1Paste your JSON Web Token (ey...) string into the left input area.
- 2If you know the symmetric secret used to sign the token (for HS256), enter it into the Verify block to cryptographically check if the token is valid.
- 3Inspect the parsed JSON structures on the right side. Any Unix timestamps like 'iat' or 'exp' will be automatically parsed into human-readable local time.
Key Benefits
- Cryptographic Verification: Utilize Web Crypto API to ensure your token signatures haven't been tampered.
- Timestamp Expansion: No more opening secondary timestamp converters; expiration states are visually flagged.
- Absolute Privacy: Handled 100% Client-Side. Your tokens or secrets are never dispatched to our networks.
What is Signature Verification?
A standard JSON Web Token (JWT) acts as an identity passport. But without checking the cryptographic stamp—the signature—there is no guarantee the passport hasn't been forged. By implementing a secure JWT verification tool inside the browser using `crypto.subtle` APIs, developers can input their `HS256` secret and securely test exactly how their token will be processed on backend servers without installing Postman dependencies.
JWT Expiration Details
Understanding token validity periods is crucial. Our debugger strictly identifies standard claims like `exp` (Expiration Time), `nbf` (Not Before), and `iat` (Issued At). It natively transforms these obscure Unix Epoch numeric stamps into your browser's localized timezone, rendering clear indicators if a token has breached its allowed lifespan.
Frequently Asked Questions
A JWT consists of 3 dot-separated base64url-encoded parts: Header (algorithm & token type), Payload (claims and user data), and Signature (verifies integrity).
Yes, on Toolioz decoding happens entirely in your browser using JavaScript. No tokens, secrets, or payloads are transmitted to any server.
HS256 uses a single shared secret key for both signing and verification. RS256 uses an asymmetric key pair: a private key for signing and a public key for verification.