Fydler UtilityBelt - JWT Generator

JWT Generator

Security & Authentication Tool

Header (JSON)

Payload (JSON)

Secret Key

Encoded JWT

About JWT

JSON Web Tokens consist of three parts separated by dots: header.payload.signature. This tool creates a JWT signed with HMAC-SHA256 using your secret key.

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lucide.createIcons(); const headerInput = document.getElementById('jwt-header'); const payloadInput = document.getElementById('jwt-payload'); const secretInput = document.getElementById('jwt-secret'); const output = document.getElementById('jwt-output'); function base64url(str) { return btoa(str).replace(/=/g, '').replace(/\+/g, '-').replace(/\//g, '_'); } async function generateJWT() { try { const header = JSON.parse(headerInput.value || '{}'); const payload = JSON.parse(payloadInput.value || '{}'); const secret = secretInput.value; if (!secret) { output.value = 'Please enter a secret key.'; return; } const headerB64 = base64url(JSON.stringify(header)); const payloadB64 = base64url(JSON.stringify(payload)); const data = headerB64 + '.' + payloadB64; const key = await crypto.subtle.importKey('raw', new TextEncoder().encode(secret), { name: 'HMAC', hash: 'SHA-256' }, false, ['sign']); const sig = await crypto.subtle.sign('HMAC', key, new TextEncoder().encode(data)); const sigB64 = base64url(String.fromCharCode(...new Uint8Array(sig))); output.value = data + '.' + sigB64; } catch(e) { output.value = 'Error: ' + e.message; } } [headerInput, payloadInput, secretInput].forEach(el => el.addEventListener('input', generateJWT)); document.getElementById('jwt-copy-btn').addEventListener('click', () => { const v = document.getElementById('jwt-output').value; if (v && !v.startsWith('Error') && !v.startsWith('Please')) { navigator.clipboard.writeText(v); showToast('Copied JWT!'); } }); function showToast(msg) { const toast = document.getElementById('toast'); const toastMsg = document.getElementById('toast-message'); toastMsg.textContent = msg; toast.classList.add('show'); setTimeout(() => toast.classList.remove('show'), 2000); }