Encoding vs verifying JWTs
Encoding assembles Base64URL header and payload (and optionally a signature). This tool helps you craft tokens for development—it does not replace a secure auth server or production key management.
JWT Encoder
Compose a JWT from JSON header and payload. Sign with HS256 and a secret, or create an unsigned (alg: none) token for local testing.
Algorithm
Used only in your browser for HS256.
How it works
- 1
Fill in the form fields the tool shows.
- 2
Change modes or toggles if available.
- 3
Copy the generated output when it looks right (often updates live).
Why use this tool
- Runs entirely in your browser — nothing is uploaded to a server.
- 100% free, no sign-up, no limits.
- Works in any modern browser — no app install, no extension, no account.
How to use JWT Encoder
Complete the fields in JWT Encoder. Output is produced in your browser from those inputs — copy it when ready.
Tips for better results
Empty optional fields if you want a minimal result. Invalid combinations should surface an error message.
Privacy and offline-friendly processing
Whenever possible, JWT Encoder processes your data locally with JavaScript in this page. That means drafts, secrets, and unfinished work stay on your device by default. Prefer this workflow when you do not want to upload sensitive text, tokens, passwords, or files to a third-party service.
Frequently asked questions
Is alg:none safe for production?
No. Unsigned tokens are for learning and local tests only. Production systems should reject alg:none.
Is my secret sent anywhere?
No. Signing uses the Web Crypto API in your browser.
Is my data uploaded when I use this tool?
For most FlyUtils tools, no. Processing happens in your browser with JavaScript. If a tool ever needs a server, that will be stated clearly on the page.
Is JWT Encoder free to use?
Yes. JWT Encoder is free, with no sign-up and no artificial usage caps for normal personal and work use.
Does JWT Encoder work on mobile?
Yes. The page is mobile-first, so you can paste input, tweak options, and copy results from a phone or tablet.