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JWT Decoder

Decode and inspect JSON Web Tokens with expiration status and claim details.

JWT Token

Paste a JWT token above to decode it

About JWT

Structure

JWTs consist of three parts: Header (algorithm & type), Payload (claims), and Signature (verification). Separated by dots.

Common Claims

Standard claims include: iss (issuer), sub (subject), exp (expiration), iat (issued at), aud (audience).

Expiration

The exp claim contains a Unix timestamp. This tool shows real-time expiration status with countdown.

Security Note

This tool only decodes JWTs for inspection. It does not verify signatures or validate token authenticity.

All decoding happens locally in your browser. No data is sent to any server.

How Jwt Decoder Works in Your Browser

The ToolsForgess JWT decoder parses JSON Web Tokens into their three constituent parts — header, payload, and signature — displaying each component in a readable, formatted view. Paste a JWT string and receive the decoded header with algorithm and type claims, the payload with all registered and custom claims, and the signature in its original format. The decoder validates token structure, checks expiration against the current timestamp, and highlights expired or malformed tokens. All parsing occurs entirely within the browser — no token data is transmitted to any server, making this tool safe for inspecting production tokens containing sensitive authentication claims. This tool is essential for developers debugging authentication flows, verifying token claims during API integration, and diagnosing token expiration issues in distributed systems.

Key Features

  • Parse the three JWT segments — header, payload, and signature — with formatted JSON output for each component. Identify the signing algorithm and token type at a glance.
  • Automatically check the exp claim against the current timestamp and flag expired tokens. Remaining time-to-live is displayed for valid tokens.
  • Display all registered claims including iss, sub, aud, iat, nbf, and exp with human-readable labels. Custom claims are listed alongside standard claims.
  • All token parsing occurs entirely within the browser. No token data is transmitted to any server, ensuring complete privacy for authentication tokens.

Frequently Asked Questions

Does the tool verify JWT signatures?
The decoder displays the signature component without verification. Signature verification requires the signing key which is not available to the decoder. Use a JWT verification library with the appropriate key for signature validation.
Can I decode expired tokens?
Yes. The decoder displays the contents of any structurally valid JWT regardless of expiration status. Expired tokens are flagged with a visual indicator showing the expiration has passed.
Does it handle JWE encrypted tokens?
The decoder handles JWS (signed) tokens only. JWE (encrypted) tokens require decryption with the private key before the payload can be read. The decoder will show the encrypted envelope for JWE tokens.
Is my token data stored during decoding?
No. All token parsing occurs entirely within the browser. Your JWT content is not transmitted to any server.

All data processing for Jwt Decoder runs 100% locally in your browser using client-side JavaScript. No data is uploaded to any server.

Technical Specification

JWT Token Decoding & Payload Inspection Engine

Overview

The ToolsForges JWT Decoder parses and displays the contents of JSON Web Tokens, revealing the header, payload, and signature components that are normally obscured by Base64 encoding. Paste a complete JWT string to receive an instantly decoded view of the token's algorithm, issuer, subject, expiration timestamp, custom claims, and signature metadata.

Feature Specifications

  • Header and Payload ParsingDecode both the JWT header and payload sections, displaying algorithm information, token type, and all embedded claims in a structured, readable format with proper JSON formatting.
  • Timestamp ConversionAutomatically convert numeric iat (issued at), exp (expiration), and nbf (not before) claims into human-readable date and time strings, making token lifecycle validation immediate.
  • Signature DisplayDisplay the encoded signature component separately for manual verification, alongside the algorithm used for signing, enabling developers to confirm token integrity.
  • Claim Validation IndicatorsHighlight expired tokens, not-yet-valid tokens, and missing required claims with visual indicators, enabling quick token validity assessment at a glance.

Architecture

The decoder uses React useState for JWT input and the browser's atob() function for Base64 decoding of header and payload sections. The parsed JSON is displayed in a formatted structure with automatic timestamp conversion and validation indicators.

Frequently Asked Questions

Can this tool verify JWT signatures?

The tool displays the signature component but does not cryptographically verify it, as signature verification requires the signing key. Use server-side verification with the appropriate key.

What JWT formats are supported?

The tool supports standard three-part JWTs (header.payload.signature) using Base64URL encoding. Both JWS and JWE token structures are recognized.

Does this work with expired tokens?

Yes. Expired tokens are decoded and displayed with a visual indicator showing that the expiration timestamp has passed. This is useful for debugging authentication issues.

Is my token data stored?

No. All JWT strings, decoded headers, payloads, and signatures are processed entirely within your browser. No authentication tokens are transmitted to external servers.