JWT Decode — What is JSON Web Token?
JWT (JSON Web Token) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. When you need to decode JWT tokens, you're extracting the header and payload data encoded in Base64URL format. JWTs are widely used for authentication, authorization, and information exchange in modern web applications.
A JWT consists of three parts separated by dots (.): Header, Payload, and Signature. Use our free JWT decoder online tool to instantly inspect any JWT token without installing software or sharing your data with servers.
Free JWT.io Alternative — Decode Tokens Online
Looking for a jwt.io alternative? jwtdecode.io offers a fast, privacy-focused way to decode JWT tokens online. Unlike other tools, we process everything in your browser — your tokens never leave your device. This makes our JWT online decoder perfect for working with sensitive production tokens.
How to Decode JWT Token Online
Decode JWT token in seconds with our free online tool. Here's how to use our JWT token decoder:
- Paste your JWT: Copy your JWT token and paste it into the input field. The token should have three parts separated by dots.
- View decoded data: The header and payload are automatically decoded and displayed as formatted JSON on the right side.
- Verify signature (optional): If you want to verify the token's authenticity, enter your secret key and select the algorithm (HS256, HS384, or HS512).
- Check status: The signature status indicator will show whether your token is valid, invalid, or not verified.
- Copy data: Use the "Copy JSON" button to copy the decoded payload to your clipboard.
All decoding and verification happens directly in your browser using JavaScript and the Web Crypto API. Your JWT tokens never leave your device, ensuring complete privacy and security.
JWT Debugger — Common Use Cases
Our JWT debugger and token decoder is perfect for developers and security professionals:
- Debugging authentication issues: Quickly inspect JWT tokens to verify claims, expiration times, and other payload data.
- API development: Test and validate JWT tokens during API development and integration.
- Security audits: Examine JWT structure and verify signatures to ensure proper implementation.
- Learning JWT: Understand how JSON Web Tokens work by decoding real examples.
- Token inspection: Check token expiration (exp), issued at (iat), and other standard claims.
- Troubleshooting SSO: Debug Single Sign-On implementations that use JWT tokens.
Why Use Our Online JWT Decoder?
While you could decode JWT manually or write a script, our online JWT decoder offers key advantages: instant decoding, no installation required, works on any device, and handles edge cases like proper Base64URL decoding. Our tool follows JWT standards (RFC 7519), ensuring accurate JWT token decode results.
With 100% browser-based processing using the Web Crypto API, your JWT tokens stay on your device and are never uploaded to any server. Whether you need to decode JWT online for debugging API responses or inspecting authentication tokens, your sensitive data remains completely private.
JWT Online — Decode Tokens Securely
Need to work with JWT online? Our decoder provides a secure environment for token inspection. Unlike command-line tools, our JWT decode online tool requires no setup — just paste your token and get instant results. Perfect for quick debugging sessions or when you need to decode JWT token online from any device.
Supported JWT Algorithms — Full Verification Support
Our JWT verifier supports all major JWT signing algorithms with real-time signature verification using the native Web Crypto API. Whether you're working with symmetric or asymmetric keys, our tool handles it all.
HMAC Algorithms (Symmetric)
HMAC algorithms use a shared secret key for both signing and verification. Ideal for server-to-server communication where both parties can securely share the secret.
- HS256 (HMAC-SHA256): Most common symmetric algorithm, 256-bit security
- HS384 (HMAC-SHA384): Enhanced security with 384-bit hash
- HS512 (HMAC-SHA512): Maximum HMAC security with 512-bit hash
RSA Algorithms (Asymmetric)
RSA algorithms use public/private key pairs. The private key signs tokens, while the public key verifies them. Perfect when you need to verify tokens without access to the signing key.
- RS256 (RSA-SHA256): Industry standard for OAuth 2.0 and OpenID Connect
- RS384 (RSA-SHA384): Enhanced RSA with 384-bit hash
- RS512 (RSA-SHA512): Maximum RSA security with 512-bit hash
ECDSA Algorithms (Asymmetric)
ECDSA (Elliptic Curve Digital Signature Algorithm) provides equivalent security to RSA with smaller key sizes, resulting in shorter signatures and better performance.
- ES256 (ECDSA P-256): Compact signatures with 128-bit security level
- ES384 (ECDSA P-384): Enhanced elliptic curve with 192-bit security
- ES512 (ECDSA P-521): Maximum ECDSA security with 256-bit security level
All verification is performed client-side using your browser's native Web Crypto API, ensuring both security and performance. For asymmetric algorithms, paste your public key in PEM or JWK format.
Understanding JWT Claims and Standard Fields
When you decode a JWT token, you'll see various claims in the payload. Here are the standard registered claims defined in RFC 7519:
- iss (Issuer): Identifies who issued the JWT token
- sub (Subject): Identifies the subject of the JWT (usually user ID)
- aud (Audience): Identifies the recipients the JWT is intended for
- exp (Expiration Time): Unix timestamp when the token expires
- nbf (Not Before): Unix timestamp before which the token is not valid
- iat (Issued At): Unix timestamp when the token was issued
- jti (JWT ID): Unique identifier for the token
Our JWT decoder displays all claims in a readable JSON format, making it easy to inspect token contents and debug authentication issues.
JWT Security Best Practices
While JSON Web Tokens are powerful, they require careful handling. Here are security best practices:
- Always verify signatures: Never trust a JWT without verifying its signature first
- Check expiration: Always validate the exp claim to prevent use of expired tokens
- Use appropriate algorithms: RS256 or ES256 are recommended for production systems
- Keep secrets secure: Never expose HMAC secrets in client-side code
- Validate claims: Check iss, aud, and other claims match expected values
- Use HTTPS: Always transmit JWTs over encrypted connections
- Set reasonable expiration: Short-lived tokens reduce the window for abuse
Use our JWT debugger to inspect tokens during development and ensure your implementation follows these security guidelines.