JWT Decoder

Decode and inspect JSON Web Tokens (JWT) instantly

What is a JWT Decoder?

A JWT (JSON Web Token) Decoder is a powerful tool that instantly decodes and displays the contents of JWT tokens used in modern web authentication. It breaks down the token into its three components—header, payload, and signature—allowing developers to inspect claims, verify expiration times, and debug authentication flows without server-side processing.

AuthenticationToken InspectionSecurity Analysis

Why Use JWT Decoder?

  • ✓
    Instant DecodingDecode JWT tokens in milliseconds without API calls.
  • ✓
    Debug Auth IssuesQuickly inspect claims and identify authentication problems.
  • ✓
    Check ExpirationSee exactly when your token expires and time remaining.
  • ✓
    100% PrivateAll processing happens in your browser—no data sent to servers.

How to Use

Decode your JWT token in three simple steps

01
🔑

Paste JWT Token

Copy your JWT token from your application, API response, or browser storage and paste it into the input field.

02
⚡

Auto Decode

The tool automatically decodes your token and displays the header, payload, and signature in a readable JSON format.

03
🔍

Inspect & Copy

Review the decoded data, check expiration status, and copy individual sections as needed for debugging.

Understanding JWT Structure

📋

Header

Contains metadata about the token including the signing algorithm (HS256, RS256) and token type (JWT).

{"alg": "HS256", "typ": "JWT"}
📦

Payload

Contains the claims—statements about the user and additional data like user ID, roles, permissions, and expiration time.

{"sub": "1234", "name": "John", "exp": 1916239022}
🔐

Signature

Ensures the token hasn't been tampered with. Created by encoding the header and payload with a secret key.

HMACSHA256(base64(header) + "." + base64(payload), secret)

Common JWT Claims

Standard fields you'll find in JWT payloads

🏢

Issuer

iss

Identifies who created and signed the token (e.g., your authentication server).

👤

Subject

sub

The subject of the token, typically the user ID or username.

🎯

Audience

aud

Identifies the recipients that the JWT is intended for.

⏰

Expiration

exp

Unix timestamp indicating when the token expires and becomes invalid.

📅

Issued At

iat

Unix timestamp indicating when the token was created.

🚫

Not Before

nbf

Token is not valid before this Unix timestamp.

Common Use Cases

🐛

Debug Auth

Troubleshoot login issues by inspecting token claims and expiration.

🧪

API Testing

Verify JWT tokens returned by your authentication APIs.

📊

Token Analysis

Understand what data your application stores in JWT tokens.

🎓

Learning

Study JWT structure and understand how modern authentication works.

Security Best Practices

Important security considerations when working with JWTs

⚠️

Never Store Secrets in JWT

JWTs are encoded (Base64), not encrypted. Anyone can decode and read the payload. Never store passwords, API keys, or sensitive personal data in JWT tokens.

🔒

Always Verify Signatures

Decoding a JWT doesn't verify its authenticity. Always verify the signature on your server using the secret key before trusting the token data.

🛡️

Use HTTPS Only

Always transmit JWT tokens over HTTPS to prevent interception. Never send tokens over unencrypted HTTP connections.

⏱️

Set Short Expiration Times

Use short expiration times (minutes to hours) and implement refresh tokens for long-lived sessions to minimize security risks.

Why Choose Our JWT Decoder

⚡

Instant Results

Decode tokens in milliseconds

🆓

No Registration

Free and unlimited usage

🔒

Client-Side Only

Your tokens never leave your browser

📱

Mobile Friendly

Works perfectly on all devices

📋

Copy Sections

Copy header, payload, or signature individually

⏰

Expiration Check

Automatic token expiration validation

📊

Claims Display

Common claims shown in readable format

🎯

Sample Token

Load example to see how it works

Explore Other Tools

🔐

JWT Encoder

Create and sign JWT tokens with custom claims and algorithms.

🔄

Base64 Converter

Encode and decode Base64 strings used in JWT tokens.

✨

JSON Formatter

Format and validate JSON data from JWT payloads.

🔑

Hash Generator

Generate secure hashes for JWT secret keys and signatures.

Frequently Asked Questions

Common questions about JWT tokens and our decoder tool.

A JWT Decoder is a tool that decodes JSON Web Tokens (JWT) to reveal their header, payload, and signature components. It helps developers inspect token contents, verify claims, and debug authentication issues without requiring server-side processing.
Yes! All decoding happens entirely in your browser using JavaScript. Your JWT token is never sent to our servers or any external service. However, remember that JWTs are only encoded (not encrypted), so avoid pasting tokens containing highly sensitive data on any public computer.
No, this tool only decodes the JWT structure. Signature verification requires the secret key or public key, which should never be shared. Always verify JWT signatures on your secure server before trusting the token data.
JWT tokens contain an "exp" (expiration) claim that specifies when the token becomes invalid. If the current time is past this expiration time, the token is considered expired and should not be accepted by your application.
JWTs follow a standard structure: Header.Payload.Signature. The header describes the token type and algorithm, the payload contains claims (user data), and the signature ensures the token hasn't been tampered with.