Online JWT Decoder & Inspector
Paste any JSON Web Token to instantly decode and inspect its header, payload, and registered claims. Standard claims like expiration (exp), issued-at (iat), and subject (sub) are automatically parsed into human-readable formats.
This is a local-only decoder — your token never leaves your browser. Important: decoding a JWT reveals its contents but does not verify its cryptographic signature.
100% Client-Side Processing & Privacy Guarantee
All processing takes place strictly inside your client browser using WebAssembly, Canvas, and Web Workers. Your files, documents, and data never leave your device and are never sent to external servers.
Technical Specifications & Browser Capabilities
Local runtime details and instant zero-server processing environment
Step-by-Step Instructions
1. Paste Your Token
Copy a JWT from your application, API response, or authentication header and paste it into the input field.
2. View Decoded Sections
The header and payload are instantly decoded and displayed as formatted JSON. Timestamp claims are converted to readable dates.
3. Inspect Claims
Review the algorithm, token type, expiration status, issuer, audience, and other registered claims at a glance.
Core Advantages & Features
Instant Local Decoding
Decodes JWTs entirely in your browser using standard Base64URL parsing. No server requests, no token logging, no external API calls.
Human-Readable Claims
Automatically converts Unix timestamps in exp, iat, and nbf claims to readable date and time formats. Highlights whether the token is currently expired.
Structured Header & Payload
Displays the decoded header (algorithm, token type) and payload (all claims) as properly formatted, syntax-highlighted JSON.
Malformed Token Handling
Gracefully handles truncated, corrupted, or non-JWT input with clear error messages instead of cryptic failures.
Security-First Design
Prominently warns that decoding does not equal verification. Never validates signatures, never suggests that decoded tokens are trusted.
Frequently Asked Questions
What is a JWT?
Is decoding a JWT the same as verifying it?
Can a JWT be decoded without a secret key?
Is it safe to paste a JWT into this tool?
What JWT claims does this tool decode?
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