⌘K

JWT Decoder

Encoded Token

Debug only — not server-side auth. Secret stays in this tab and is not saved.

Signature not checked.

160 chars HS256 algorithm

This tab only decodes the token. The signature is not checked unless you paste an HMAC secret. That check is debug-only — it is not server-side authentication. Nothing is uploaded.

algHS256
Issued: 1/18/2018, 1:30:22 AM
  • sub — Subject — the user or entity1234567890
Header
{
  "alg": "HS256",
  "typ": "JWT"
}
Payload
{
  "sub": "1234567890",
  "name": "Ada Lovelace",
  "iat": 1516239022
}
Signature
SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c

Developer Tools

JWT Decoder

Decode JWTs locally — inspect claims and optionally check HS256 HMAC — free, private and running entirely in your browser

Read the header and payload of a JSON Web Token, including the issued-at and expiry timestamps rendered as readable dates. Decoding happens in your browser, so a token from a live session is not transmitted anywhere.

About JWT Decoder

What it does

The decoder splits the token, Base64URL-decodes the header and payload, and displays both as formatted JSON alongside the standard claims. You can optionally check HS256/HS384/HS512 with a secret in this tab — that is debug-only, not server-side authentication. RSA/ECDSA are not verified here.

Who it is for

For backend developers debugging authorisation, QA engineers checking why a request returns 401, and support staff confirming when a token expired.

When to use it

Use it when a request is rejected and you need to see the claims the server received, or to confirm whether a token has simply expired.

Key features

  • Decode JWTs locally

    Decode your jwts locally in a single step with instant, reliable output.

  • Private by design

    Your jwts locally is processed on your device and is never uploaded or stored.

  • Instant results

    No queues, no round-trips to a server — output updates as fast as you type.

  • Copy, download, share

    Export your result in one click or copy it straight to the clipboard.

  • Keyboard-first workspace

    Shortcuts and a focused layout keep you moving without touching the mouse.

  • Works on every device

    A responsive layout that stays usable on desktop, tablet and phone.

  • Light and dark themes

    A comfortable, high-contrast interface for long working sessions.

How to use JWT Decoder

  1. 1Open JWT Decoder on TheToolSera — nothing to install and no account required.
  2. 2Paste, type or upload your jwts locally.
  3. 3Choose the options you need so the output matches your workflow.
  4. 4Run decode and review the result in the workspace.
  5. 5Check the highlighted details to confirm everything looks correct.
  6. 6Copy the output, download it, or continue with a related developer tool.

Example

Before

eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiIxMjMiLCJuYW1lIjoiQWRhIn0...

After

{ "alg": "HS256" }  ·  { "sub": "123", "name": "Ada" }

Header, payload and expiry are decoded locally — the token is never sent anywhere.

Common problems and fixes

  • The token will not decode

    A JWT has three dot-separated parts. Truncated copies from logs are the usual cause.

  • Expiry looks wrong

    The exp claim is in seconds since the Unix epoch, in UTC. Compare it against UTC, not local time.

Benefits

  • Save time

    What used to take a script or a desktop app now takes seconds — decode jwts locally the moment the page loads.

  • Stay private

    Nothing is uploaded. JWT Decoder runs client-side, which keeps confidential jwts locally on your own machine.

  • Get accurate output

    Deterministic processing and clear error reporting mean the result you see is the result you ship.

  • Work anywhere

    Once loaded, JWT Decoder keeps working offline and on any modern browser, desktop or mobile.

Common use cases

  • Backend developers

    Inspect and clean up jwts locally returned by an API before wiring it into a service.

  • Frontend developers

    Prepare fixtures and mock jwts locally for components without leaving the browser.

  • QA engineers

    Reproduce a defect by checking the exact jwts locally a failing request produced.

  • Data analysts

    Reshape exported jwts locally into a structure a spreadsheet or notebook can read.

  • DevOps engineers

    Sanity-check configuration jwts locally before rolling a change out to production.

  • Students

    Learn how jwts locally is structured with immediate, visual feedback while experimenting.

Tips & best practices

  • Keep a small sample of your jwts locally handy — testing the options on a short input is faster than reworking a large one.
  • Use the copy and download actions instead of selecting text manually; they preserve formatting exactly.
  • Bookmark JWT Decoder so the workspace is one keystroke away during your next session.
  • Format jwts locally before diffing or committing it — consistent formatting keeps reviews focused on real changes.
  • Use JWT Decoder alongside your editor: paste, transform, copy back, and skip writing a throwaway script.

Common mistakes to avoid

  • Pasting partial jwts locally and assuming the result is wrong — always include the full input.
  • Ignoring the status messages in the workspace; they explain exactly what went wrong and where.
  • Uploading sensitive jwts locally to random online services — JWT Decoder never needs to, because it runs on your device.
  • Copying jwts locally out of a terminal with wrapped lines, which silently corrupts the input.
  • Trusting a transformed result without re-validating it once more before shipping.

Frequently asked questions

Does it verify the signature?

It always decodes without a key. You can optionally check HS256, HS384 or HS512 with a secret you paste — that is debug-only and not a substitute for server-side auth. RS256/ES256 are not verified here.

Is it safe to paste a production token?

The decoding runs locally in your browser, but treat any live token as a credential and prefer an expired or test token where possible.

Is JWT Decoder free to use?

Yes. JWT Decoder is completely free with no sign-up, no watermark and no daily limits.

Does JWT Decoder upload my jwts locally?

No. All processing runs in your browser with JavaScript, so your jwts locally never reaches a server.

How do I decode jwts locally online?

Open JWT Decoder, add your jwts locally, adjust the options if needed, and the result appears instantly — then copy or download it.

Do I need to install any software?

No installation is required. JWT Decoder loads in any modern browser on Windows, macOS, Linux, Android and iOS.

Can I use JWT Decoder offline?

Yes. Because the tool is client-side, it continues to work once the page has loaded, even without a connection.

Is there a size or usage limit?

There is no enforced limit. Very large inputs depend only on your device's available memory, since everything is processed locally.

Does it work on mobile?

Yes. The layout is responsive, so JWT Decoder is fully usable on phones and tablets as well as desktop.

Is my data stored or shared with anyone?

Never. TheToolSera has no server-side processing for this tool and does not log, store or sell your jwts locally.

Does JWT Decoder support large files?

Yes. JWT Decoder streams jwts locally through your browser's engine, so the practical limit is your device's memory rather than a server quota.

Can I use JWT Decoder in a commercial project?

Yes. Output produced by JWT Decoder is yours to use in personal, academic and commercial work at no cost.

Conclusion

JWT Decoder gives you a fast, private and dependable way to decode jwts locally — inspect claims and optionally check hs256 hmac without installing anything. Because every calculation and conversion happens in your browser, you get instant results while your jwts locally stays on your machine. Try it above, then explore the rest of TheToolSera's developer tools to complete the next step in your workflow.

Ready to try JWT Decoder?

Scroll back up to start now, or continue with another free developer tool.

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