> ## Documentation Index
> Fetch the complete documentation index at: https://docs.replyke.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Sign Testing JWT

> Generate a signed RS256 JWT for development and testing

Signs a short-lived JWT (5 minutes) using your project's RSA private key. Use this during development to generate tokens for testing [external auth](/sdk/authentication/external) without needing to implement JWT signing in your test environment.

<Warning>
  Never use this endpoint in production. It requires your RSA private key in the request body, which must be kept secret. Use it only in local development or CI environments.
</Warning>

## Body Parameters

<ParamField body="privateKey" type="string" required>
  Your RSA private key encoded as a Base64 string. This is the private key associated with the public key configured in your project's external auth settings.
</ParamField>

<ParamField body="payload" type="object" required>
  The JWT payload. Must include at least an `id` field (the user's ID in your system). All fields are included in the `userData` claim.

  ```json theme={null}
  {
    "id": "user-123",
    "email": "alice@example.com",
    "name": "Alice"
  }
  ```
</ParamField>

<ParamField body="projectId" type="string">
  The project ID. Can be provided in the body or as a URL path parameter (`:projectId`). The body value takes precedence if both are provided.
</ParamField>

## Response

Returns the signed JWT as a plain text string (not JSON):

```
eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...
```

The JWT is signed with `RS256`, expires in 5 minutes, and includes:

* `sub` — the user's `id` from the payload
* `iss` — the project ID
* `aud` — `"replyke.com"`
* `userData` — the full payload object

## Error Responses

<AccordionGroup>
  <Accordion title="Missing Parameters — 400">
    ```
    Missing params in request body
    ```

    Returned when `projectId`, `privateKey`, or `payload` is missing.
  </Accordion>

  <Accordion title="Missing User ID — 400">
    ```json theme={null}
    { "error": "Missing user id in payload.", "code": "crypto/missing-params" }
    ```

    Returned when the `payload` object does not include an `id` field.
  </Accordion>
</AccordionGroup>