Webhook HMAC Signer
Sign and verify GitHub, Stripe, and Slack webhook signatures locally.
OpenVerify HS256 JWT signatures locally with your secret. - runs entirely in your browser. Free, fast and private.
Add the token you want to validate locally.
Provide the shared secret used to sign the token.
HMAC is recomputed in-browser and compared to the token.
Invalid signature or expiry shows a clear error state.
Decoding a JWT tells you what claims say. JWT Verify asks a harder question: does this HS256 signature match the secret you hold, computed locally with Web Crypto?
Verify when you are debugging an API that rejects tokens, comparing staging vs production secrets, or teaching how signature checks work without pasting secrets into a hosted debugger. Only HS256-style shared-secret checks belong here. Asymmetric algs need your own key material in application code.
Pitfall: verifying with the wrong secret and assuming the token is forged. Confirm environment first. Never paste production secrets into a browser on a shared machine.
Tip: decode claims first so you know alg is HS256 before you verify.
The secret and token stay in your browser for the HMAC check. OneDevToolkit does not receive your signing key to perform verification.
Pair with: JWT Decoder · Decode JWTs safely
Processes data instantly with no server round-trips.
Your data never leaves your browser. Nothing is uploaded.
Works in any modern browser. Nothing to download or install.
No limits, no sign-up, no credit card required.
Works on desktop, tablet and mobile devices.
Beautiful in both themes. Your preference is saved.
Keyboard shortcut
Confirm HS256 tokens against the secret your service uses.
See whether staging tokens fail because the secret differs.
Show valid vs tampered payloads without a cloud JWT site.
Answers for this tool. For site-wide help, open the FAQ hub.
JWT Verify Verify HS256 JWT signatures locally with your secret. It runs entirely in your browser with instant feedback.
No server upload is required for formatting/validation. Clearing the page removes the text from memory.
Validators report problems; formatters beautify valid structure. Severely broken input may need manual fixes first.
Formatters and converters aim to preserve meaning. Always review diffs for mission-critical code before committing.
Paste smaller chunks if the tab slows down. Minifiers and deep validators scale with input size on the CPU you have.
Many tools support Ctrl/⌘+Enter to run and standard copy shortcuts. Check the tool toolbar for Sample / Clear / Download.
When options exist (spaces vs tabs, indent width), set them before copying output into your repo to match project style.
After the page loads, formatting continues offline. CDN libraries need an initial network load.
Bookmark JWT Verify, copy output into editors, or chain steps with Recipes.