JWT Token Decoder & Expiration InspectorRFC 7519 Compliant
Inspect Header, Payload, Signature, decode exp timestamp with 100% privacy. Zero server requests, completely isolated in your browser.
Provide the shared secret to verify HMAC (HS256/384/512) signatures locally using the browser's Web Cryptography API. Zero secret data ever leaves your computer.
Paste or load a token on the left to inspect expiration & claims.
100% Client-Side Privacy
Every JWT decoding and expiration calculation is performed purely in your browser's memory using native JavaScript and Web APIs. Zero token data or cryptographic secrets are ever sent to backend servers.
Precision Expiration Clock
Real-time countdown inspection for exp, iat, and nbf timestamps. Includes localized calendar format, UTC timestamps, and visual lifetime progress indicators with second-level accuracy.
Local WebCrypto HMAC Verify
Verify HS256, HS384, and HS512 signatures directly inside your client environment using the W3C Web Cryptography API, preventing accidental disclosure of staging or production credentials.
Frequently Asked Questions & JWT Guide
Everything you need to know about JSON Web Token security, anatomy, and offline verification.
Is it safe to paste production JWT tokens into this decoder?
Yes! Unlike traditional web tools that transmit payloads to remote servers, ToolsAA operates on a 100% Client-Side Privacy architecture ('use client'). You can inspect your browser's Network tab to confirm zero HTTP requests or telemetries occur during decoding.
What is the difference between encoding and encryption?
Standard JWTs are Base64URL-encoded, not encrypted. This means anyone who intercepts the token can read the Header and Payload claims. The signature only ensures tamper-evidence, not secrecy. Never store plain passwords or sensitive PII in standard JWT claims!
How are the exp, iat, and nbf timestamps represented?
RFC 7519 specifies that NumericDate claims (exp, iat, nbf) are Unix epoch timestamps expressed in seconds (not milliseconds). Our inspector translates these into your local machine timezone and UTC ISO strings automatically.
Why does signature verification require a secret or certificate?
The signature is calculated as HMACSHA256(base64Url(header) + '.' + base64Url(payload), secret). Without the correct shared secret (for HMAC) or public certificate (for RSA/ECDSA), the signature cannot be validated.