🔑 JWT Decoder

📝 Encoded Token

🛡️ Verify Signature (HS256 HMAC-SHA256)

Enter a secret key to verify the signature.

📋 Decoded Claims

Header: Algorithm & Token Type HEADER

{}

Payload: Data claims PAYLOAD

{}

Signature Metadata SIGNATURE

Paste a token to inspect signature details.

JWT Decoder – Decode JSON Web Tokens Online

JWT Decoder is a developer utility that allows you to decode, verify, and examine JSON Web Tokens (JWT) in real-time. Paste your encoded JWT into the workspace to immediately decode its header, payload claims, and signature details.

How does the local JWT Decoder work?

Unlike online decoders that upload token data to backend APIs, this tool is 100% client-side. The decoding algorithm runs completely inside your browser sandbox using JavaScript. Your authentication tokens, API credentials, and user profile payloads are never sent over the network, ensuring absolute confidentiality.

Key Features:

📝 Real-time Decoding: Token parts (Header, Payload, Signature) are parsed and updated instantly as you type.
🧩 JSON Formatting: The decoded header and payload claims are automatically formatted with proper syntax highlighting.
🛡️ HMAC Signature Verification: Enter your HS256 secret key to verify the integrity and signature authenticity of your token locally using the Web Crypto API.
📅 Timestamp Formatting: Automatically parses standard claim fields such as Issued At (iat), Expiration Time (exp), and Not Before (nbf) into readable human-formatted local dates and time intervals.

Where are JWTs used?

JSON Web Tokens are heavily used in modern web applications for stateless authentication and authorization. When a user logs in, the authentication server issues a signed JWT containing user identities and permissions. The client includes this token in subsequent API requests (typically in the Authorization: Bearer header), allowing backend servers to verify identity without querying a central session database.

Frequently Asked Questions

Yes. All parsing, base64 url-decoding, and cryptographic verification processes happen in memory inside your browser. No data leaves your computer.

Decoding simply exposes the claims stored inside the base64-encoded strings. To guarantee that the token has not been altered, you must verify the signature. You can do this in the signature verification panel of our tool by entering the HS256 secret key.