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JWT Generator

100% Free

Sign HMAC JWTs (HS256/HS384/HS512) for API testing — secret, payload, algorithm, signed token. Pairs with the JWT Decoder for round-trip verify.

Real-time
Client-Side
RFC 7519
Algorithm

Standard claims: iss, sub, aud, exp, nbf, iat, jti.

The secret never leaves your browser. Use ≥ 32 random bytes for HS256, ≥ 48 for HS384, ≥ 64 for HS512.

Signed JWT
Enter payload and secret…

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How to Use

  1. 1 Pick HMAC algorithm — HS256 (default), HS384, or HS512
  2. 2 Paste or write your JSON payload (must be a JSON object)
  3. 3 Enter the shared secret used to sign the token
  4. 4 The signed JWT updates instantly as you change inputs
  5. 5 Copy and paste into Postman / curl Authorization header

Features

  • All three HMAC algorithms (HS256/HS384/HS512)
  • Real-time signing as you type
  • Standard claim placeholders (iss, sub, aud, exp, nbf, iat, jti)
  • Custom header claims (e.g., kid for key rotation)
  • Round-trip verifiable with the JWT Decoder
  • Uses Web Crypto subtle.sign — same primitive as Node `crypto`

Why it Matters

Backend API tests need real JWTs. Spinning up a Node script with `jsonwebtoken` for every test fixture is overkill — most of the time you just want a quick token for one experiment. This tool produces RFC 7519-compliant tokens in milliseconds, and they verify against any conforming JWT library.

★★★★★

Use Cases

API Testing

Mint a quick token to test a protected endpoint

Webhook Signing

Generate signed payloads to test webhook handlers

OAuth Mock

Build a test JWT with custom scopes / roles

Frequently Asked Questions

Does this support RS256 or ES256 (asymmetric algorithms)?
No — only HMAC algorithms (HS256/HS384/HS512). RS256/ES256 require keypair management which makes more sense server-side. For asymmetric tokens use a Node CLI.
How long does the token last?
Forever, unless you set an `exp` claim in the payload. Add `"exp": <unix-seconds>` to set an expiry — for example, `Math.floor(Date.now()/1000) + 3600` for 1 hour.
Is my secret safe?
Yes — signing happens entirely in your browser via Web Crypto. The secret never leaves your device. Don't paste real production secrets into any tool you don't fully trust though.
How is HS256 different from HS512?
Both are HMAC, just with different SHA-2 hash functions. HS512 produces a longer signature (86 vs 43 chars) and is marginally more secure, at the cost of a slightly larger token. HS256 is the default for most JWT libraries.
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Want to learn how this works?

Browse all guides →
How to Use JWT Generator
jwt

How to Use JWT Generator — Complete Guide

Learn how to create signed JWT tokens for testing and development using Tools.Town's free JWT Generator.

8 May 2026

5 min read

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