100% Client-Side

JWT Builder

Free online JWT builder. Create and sign JSON Web Tokens with custom payloads using HS256 via Web Crypto. 100% client-side. — runs 100% in your browser, client-side only. No data is sent to any server. Free to use, no account required.

Free Client-Side No Login No Storage
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JWT Decoder & Inspector Decode and inspect JWT tokens — header, payload, claims at a glance JWT Encoder Create and sign JWT tokens with custom claims and headers HMAC Generator Generate HMAC message authentication codes — SHA256, SHA512, SHA1, MD5

How to Use the JWT Builder

  1. Edit the JSON payload with your claims (sub, iat, exp, etc.).
  2. Choose HS256 or none (unsigned).
  3. Enter a secret key for HS256.
  4. Click Sign JWT.

Uses Web Crypto HMAC-SHA256 for signing. No data leaves your browser.

What is JWT Builder?

A JWT builder creates JSON Web Tokens by assembling header, payload, and signature. You specify claims (sub, exp, iat, etc.), choose the algorithm, and provide a signing key to generate valid tokens.

Why Use This Tool

Testing authentication systems requires generating JWTs with specific claims. A builder lets developers create test tokens without writing signing code or setting up auth infrastructure.

When to Use It

Use JWT builder when testing authentication flows, creating tokens for development environments, learning JWT structure, or generating tokens with specific claims for debugging.

Who Should Use It

Backend developers, QA engineers, identity teams, and API consumers testing auth contract behavior.

How to Use the JWT Builder

  1. Define header algorithm and token type.
  2. Add payload claims such as sub, iss, aud, iat, and exp.
  3. Select signing method (HS256/RS256) and provide key material.
  4. Generate token, test in your API, and verify claims during decode.

Security note

Never include secrets in JWT payloads. Keep expiration short and protect signing keys in secure key management.

Common Uses

  • Creating test tokens for development
  • Testing authentication flows
  • Debugging JWT-based systems

Frequently Asked Questions

Is it safe to generate JWTs online?

CipherKit generates JWTs entirely in your browser. Your secret key never leaves your device. For production secrets, this is safer than server-based tools.

What's the difference between HS256 and RS256?

HS256 uses a shared secret for signing and verification. RS256 uses asymmetric keys — private to sign, public to verify. RS256 is better when verifiers shouldn't have signing ability.

Which claims should I include?

Standard claims: sub (subject), exp (expiry), iat (issued at), iss (issuer). Add custom claims as needed. Always include exp to limit token lifetime.