Toolstack
100% Client-Side JSON Web Token Inspector

Online JWT Decoder

Inspect JSON Web Tokens with color-coded syntax formatting, expiration timers, and standard claim analysis—100% locally in browser memory.

100% Local Browser Execution Guarantee

Unlike other online decoders that log sensitive access tokens to external servers, Toolstack decodes 100% locally in your browser memory. Your secrets, bearer tokens, and user claims never leave your device.

Demo:
ACTIVE & VALID2315h 34m remaining
Alg: HS256Type: JWT

Header: Algorithm & Token Type

{
  "alg": "HS256",
  "typ": "JWT"
}

Payload: Data & Claims

{
  "sub": "1234567890",
  "name": "Alex Morgan",
  "email": "alex@example.com",
  "roles": [
    "user",
    "admin"
  ],
  "iat": 1738800000,
  "exp": 1799900000
}

Signature

k4Z7xQZ9wK5P8rT2vM1nY3bL0sF6hJ9dG4aC2eX8vU0

Your Base64 data stays in your browser. Client-side only

How JSON Web Tokens (JWT) Work: Structure & Claims

A JSON Web Token (JWT) specified in RFC 7519 is an open, industry-standard RFC method for securely representing claims between parties. A typical token contains three parts separated by periods (.):

1

Header (Red)

Specifies the cryptographic algorithm (HS256, RS256, ES256) and token type.

2

Payload (Purple)

Contains registered claims such as issuer (iss), expiration (exp), subject (sub), and custom roles.

3

Signature (Cyan)

Used by the receiving backend to verify message integrity and ensure the sender is authentic.

Critical Security Alert: Signed Does Not Mean Encrypted

Standard JSON Web Tokens are signed, but not encrypted. The payload is readable by anyone who inspects the HTTP Authorization header. Never place database passwords, API master secrets, or unencrypted private data inside a JWT payload.

Zero-Server Security Guarantee

Unlike online JWT tools that transmit tokens to remote backends for telemetry, Toolstack runs 100% locally in your browser memory. Your production OAuth credentials and user tokens are never exposed.

Frequently Asked Questions

Clear, concise answers to common questions about Base64 decoding, encoding, and specifications.

A JSON Web Token (RFC 7519) is a compact, URL-safe means of representing claims between two parties. It is composed of three Base64URL-encoded parts separated by dots: Header, Payload, and Signature.

Explore More Free Tools on Toolstack

Client-side developer utilities, image converters, calculators, and educational engineering guides.

Word Counter

Count words, characters with/without spaces, sentences, and paragraphs in real time with reading speed metrics.

Open Tool

PDF Compressor

Reduce PDF document file size directly in your browser with zero server uploads.

Open Tool

Image Compressor & Resizer

Batch compress and scale JPG, PNG, and WebP images with custom quality settings.

Open Tool

URL Encoder & Decoder

Encode and decode query strings, special characters, and parameters with RFC 3986 percent-encoding.

Open Tool

JSON Validator & Formatter

Beautify, validate, minify, and auto-fix JSON syntax errors with real-time line/column diagnostics.

Open Tool

HEIC to JPG Converter

Convert Apple iPhone HEIC and HEIF photos to high-quality JPG directly in your browser.

Open Tool