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JWT Decoder Online

JWT decoder without verification. Safely decode JWT tokens to inspect Header and Payload. Read-only — no signature validation. Your tokens stay in your browser.

Your inputs remain on your device.

Decode JWT Token

A valid JWT has three parts separated by dots (xxx.yyy.zzz).

Parse JWK / JWKS

Paste a JSON Web Key (JWK) or a JSON Web Key Set (JWKS) to inspect its structure.

How It Works

When to Use This Tool

  • 1Debug authentication issues by inspecting JWT token contents
  • 2Verify token expiration dates and issued-at timestamps
  • 3Inspect custom claims and permissions embedded in tokens
  • 4Parse JWK/JWKS for key management and verification setup

Security Tips

  • ✓This tool only decodes JWTs—it does NOT verify signatures
  • ✓Don't trust a JWT without proper signature verification on your server
  • ✓Always use HTTPS when transmitting JWTs to prevent interception
  • ✓Validate all claims (iss, aud, exp) before accepting a JWT

What is JWT?

JSON Web Token (JWT) is an open standard (RFC 7519) that defines a compact and self-contained way for securely transmitting information between parties as a JSON object. This information can be verified and trusted because it is digitally signed using a secret (with the HMAC algorithm) or a public/private key pair (using RSA or ECDSA).

JWTs are commonly used for authentication and information exchange in modern web applications. When a user logs in, the server generates a JWT containing the user's identity and permissions. The client then includes this token in subsequent requests, allowing the server to verify the user's identity without maintaining session state.

The key advantage of JWT is its stateless nature—the server does not need to store session information in a database. All necessary information is contained within the token itself, making JWT ideal for distributed systems and microservices architectures.

JWT Structure

A JWT consists of three parts separated by dots ("."): Header, Payload, and Signature. Each part is Base64Url encoded.

1Header

Contains metadata about the token, including the signing algorithm (alg) and token type (typ).

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

2Payload

Contains the claims—statements about the user and additional data. Claims are categorized as registered (standard), public, or private.

{
  "sub": "1234567890",
  "name": "John Doe",
  "iat": 1516239022,
  "exp": 1516242622
}

3Signature

Ensures the token has not been tampered with. Created by signing the encoded header and payload with a secret key.

HMACSHA256(
  base64UrlEncode(header) + "." +
  base64UrlEncode(payload),
  secret)

Standard JWT Claims

iss

Issuer - Identifies the principal that issued the JWT

sub

Subject - Identifies the principal that is the subject of the JWT

aud

Audience - Identifies the recipients that the JWT is intended for

exp

Expiration Time - The time on or after which the JWT must not be accepted

nbf

Not Before - The time before which the JWT must not be accepted

iat

Issued At - The time at which the JWT was issued

jti

JWT ID - Unique identifier for the JWT

Common Use Cases

Authentication

After user login, the server issues a JWT that the client stores and sends with each request, eliminating the need for server-side session storage.

Information Exchange

Securely transmit information between services. The signature ensures the data has not been tampered with during transit.

API Authorization

Third-party applications can access APIs on behalf of users using JWT-based OAuth 2.0 flows, with granular permission scopes.

Single Sign-On (SSO)

Users authenticate once and gain access to multiple applications without re-entering credentials, with JWTs carrying identity assertions.

Security Considerations

!

This Tool is Read-Only

This decoder only parses and displays JWT contents. It does NOT verify signatures. Don't trust a JWT without proper signature verification on your server.

!

Use HTTPS Always

JWTs contain sensitive information. Always transmit them over HTTPS to prevent interception and token theft.

!

Set Short Expiration

Include an exp claim with a short validity period (e.g., 15 minutes). Use refresh tokens for extended sessions.

!

Validate All Claims

Validate the issuer (iss), audience (aud), and other relevant claims before accepting a JWT.

!

Secure Storage

Store JWTs securely. In browsers, use httpOnly cookies when possible. Avoid storing sensitive tokens in localStorage for production applications.

Related Tools

Base64 Encoder

Encode/decode Base64 data

SHA-256 Hash

Generate secure hashes

HMAC Calculator

Calculate message authentication codes

JSON Formatter

Format and validate JSON

References

Your inputs remain on your device.