Developer Tools

JWT Decoder & Claims Inspector

Secure, client-side JSON Web Token parser. Inspect headers, payload claims, and sign HMAC signatures instantly in full privacy.

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PASTE ENCODED JWT TOKEN

Inspection Workspace

Paste an encoded JWT on the left to inspect its parameters, decode payloads, and verify signatures instantly.

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What is a JSON Web Token?

JSON Web Tokens (JWT) are an open standard (RFC 7519) that defines a compact, URL-safe way to securely transmit structured data between client and server as a JSON object.

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Encoding vs. Cryptographic Verification

Encoding formats JSON payload claims into a URL-safe Base64url string. Cryptographic Verification, however, validates that the token was signed with a HMAC secret or public key and has not been tampered with.

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Who Uses JWTs and Why?

Modern engineering teams use JWTs for stateless authentication (Single-Sign-On), API authorization, and secure information exchange. They operate completely offline on the client side with no database lookup overhead.

JWT, Base64, and URL Encoding Explained

Demystify data encoding formats. Learn how JSON Web Tokens work, when to use Base64, URL encoding, Hex, Binary, and Unicode standards to transmit and structure backend data safely.

Read the Complete Guide➔

Overview & Capabilities

Decode, inspect, and analyze JSON Web Tokens (JWT) with our client-side JWT Decoder! Paste any JWT string to instantly parse its Header, Payload claims, expiration timestamps (exp, iat, nbf), signature algorithm (RS256, HS256, ES256), and human-readable time-to-expiry indicators with 100% offline privacy.

Tutorial

How to Use

Paste your encoded JWT token (in standard header.payload.signature format) into the input box.

View color-coded segmentation: Red for Header, Purple for Payload, and Cyan for Signature.

Inspect the decoded JSON Header (algorithm and token type) and Payload claims on the right.

Review the Token Expiration status badge (Active vs Expired) and relative time remaining.

Copy formatted JSON payloads or inspect standard OAuth2/OIDC claims (sub, iss, aud, scope).

Capabilities

Key Features

Color-Coded Token Segmentation: Distinguishes Header, Payload, and Signature components with standard syntax colors.

Live Expiration Time Counter: Translates Unix epoch timestamps (exp, iat) into local dates and relative countdown timers.

Standard Claims Reference Guide: Explains core RFC 7519 claims including iss (Issuer), sub (Subject), aud (Audience), and exp.

Algorithm Signature Identifier: Identifies asymmetric (RS256, ES256, EdDSA) and symmetric (HS256, HS512) algorithms.

Client-Side Token Parser: Decodes claims directly inside browser RAM.

Applications

Common Use Cases

API Debugging: Quickly verifying the claims and scopes in your Authorization header tokens.

Security Auditing: Checking if tokens have correct expiration and audience values.

Development: Inspecting OAuth2 and OIDC tokens during integration.

Learning: Understanding how JWTs work and what common claims represent.

Privacy-Conscious Workflow: Decoding production tokens without sending them to third-party servers.

Guidance

Tips & Best Practices

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JWTs are Base64Url encoded, not encrypted. Never store sensitive secrets in the payload.

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Always check the alg header to ensure it matches your expected algorithm (e.g., RS256).

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The exp claim is in seconds (Unix time). Our tool converts this for you automatically.

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If a token fails to decode, ensure you haven't included the "Bearer " prefix from the Auth header.

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Use the History Tape to switch between access and refresh tokens during debugging.

Ecosystem

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Answers

Frequently Asked Questions

Q Is it safe to paste production JWT tokens containing credentials into this decoder?

Yes, 100%. All decoding operations run locally in your browser's JavaScript sandbox. No tokens, secret claims, or authorization credentials are ever sent to external servers.

Q What are the three parts of a JSON Web Token?

A JWT consists of three Base64URL-encoded parts separated by dots: 1. Header (algorithm and token type), 2. Payload (claims and user data), 3. Signature (cryptographic hash validating token authenticity).

Q How does the decoder check if a JWT has expired?

The decoder reads the numeric `exp` (expiration) timestamp from the payload, converts it from Unix epoch seconds to milliseconds, and compares it against `Date.now()`.