JWT Claims Builder

Assemble JWT payload objects with standard RFC 7519 claims.

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Input
Output
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About jwt claims builder

JWT Claims Builder keeps its state in memory and nowhere else. That is why it forgets everything on reload, and why it cannot leak anything.

There is no account and no upload step. Whatever you paste lives in a variable until you close the tab, and then it does not.

You will find it under Tokens, alongside 9 other tools for the same sort of job.

Supports iss, sub, aud, exp, iat, jti claims plus custom key-value pairs.

How to use it

01
Start it
Every control is on the tool itself. Keyboard shortcuts, where there are any, are listed beside it.
02
Watch it run
It updates in the page as you go. Nothing is sent anywhere, so it keeps working with the network off.
03
Close when done
Nothing is stored between visits. Reloading gives you a clean start rather than picking up where you left off.

Examples

API service token with RBAC claims
Build claims for an API access token with role and permissions
Input
issuer: https://auth.example.com
subject: user-12345
audience: https://api.example.com
expiresInMinutes: 30
includeIat: true
includeJti: false
customClaims: {"role":"admin","permissions":["read","write"]}
Output
{
  "iss": "https://auth.example.com",
  "sub": "user-12345",
  "aud": "https://api.example.com",
  "exp": 1787565981,
  "iat": 1787564181,
  "role": "admin",
  "permissions": [
    "read",
    "write"
  ]
}

Questions

Does JWT Claims Builder work offline?+

Yes. It is JavaScript running in this tab, so once the page has loaded it needs nothing further from the network. Put the machine in flight mode and it carries on. Nothing you do here is sent anywhere, because there is nowhere for it to go.

Does it remember anything between visits?+

No. Reload the page and it starts from nothing. There is no account, no saved state and no cookie holding your last session. That is a deliberate trade: it cannot lose your data because it never keeps any.

Is it accurate?+

Timing comes from performance.now(), the high resolution clock the browser provides, rather than from setInterval, which drifts by a few milliseconds every tick and compounds over minutes. What can still shift things is the browser throttling a tab in the background, so leave it visible if the timing matters.

Does it make a sound?+

Where a sound makes sense, it is generated with the Web Audio API rather than loaded as a file, so there is nothing to download and nothing to block. Browsers refuse to start audio until you have interacted with the page, which is why the first press is what switches it on.

Can I use JWT Claims Builder on a phone?+

Yes. The controls are sized for touch and the layout collapses to one column on a narrow screen. Bear in mind that a phone locking its screen will suspend the page, and timing stops with it.