About JWT Debugger & Security Token Inspector
Secure, browser-native JSON Web Token (JWT) debugger and token inspector. Inspects and decodes JWT header, payload claims, and signatures in real time. Features color-coded token parsing (Header, Payload, Signature), Base64Url decoding, human-readable timestamp conversions for exp, iat, and nbf claims with live expiration status countdown, and in-browser signature verification using the native Web Crypto API (crypto.subtle) without transmitting sensitive bearer tokens or secret keys over the internet.
Key Capabilities & Features
- Color-coded JWT token decomposition (Header in rose, Payload in purple, Signature in cyan)
- Zero-leak client-side HMAC-SHA256 (HS256) signature verification via native crypto.subtle
- Automatic expiration inspection with human-readable relative time and UTC timestamps
- One-click sample presets: standard active user token, expired session token, and admin claims
- Instant formatted JSON editing and syntax validation
- One-click copy for clean tokens and decoded claim JSON
How to Use JWT Debugger & Security Token Inspector
Paste JWT Token
Paste any three-part bearer token (eyJhbGci...) into the encoded input editor.
Inspect Claims & Header
View decoded JSON claims, user roles, email, issuer, and token algorithm in real time.
Verify Signature
Type your secret key to verify the HMAC-SHA256 cryptographic signature in browser memory.
Check Expiration
Inspect the live expiry countdown badge to see if the token is valid or expired.
Privacy & In-Browser Execution Guarantee
100% Client-Side. Your JWT tokens, user claims, and secret signing keys execute strictly in browser memory with zero server uploads.
Frequently Asked Questions
Is it safe to paste sensitive production JWTs into this tool?
Yes! Unlike popular online debuggers that transmit tokens to cloud servers, NEOKYRU executes all Base64Url decoding and HMAC cryptographic validation strictly inside your browser's local JavaScript memory with zero network requests.
Which signing algorithms can be verified?
The tool decodes headers and payloads for all JWT algorithms (HS256, HS384, HS512, RS256, ES256) and provides in-browser live cryptographic signature verification for HMAC-SHA256 via the Web Crypto API.