Skip to main content

​
Overview

Returns a function that calls the Replyke API to sign a JWT using your project’s private key. This is intended exclusively for development and testing of external authentication flows — it lets you generate valid user JWTs from the client without setting up a backend.
Never use this hook in production. Calling this function exposes your project’s private key in client-side code, which is a critical security vulnerability. In production, JWT signing must happen on your backend server. See the External Authentication guide.

​
Usage Example

import { useSignTestingJwt } from "@replyke/react-js";
import { useAuth } from "@replyke/react-js";

function DevAuthHelper() {
  const signTestingJwt = useSignTestingJwt();
  const { signInWithToken } = useAuth();

  const signInAsTestUser = async () => {
    const token = await signTestingJwt({
      projectId: "your-project-id",
      privateKey: "your-private-key", // ⚠️ Development only
      userData: {
        id: "external-user-123",
        name: "Test User",
        email: "test@example.com",
      },
    });

    if (token) {
      await signInWithToken(token);
    }
  };

  return <button onClick={signInAsTestUser}>Sign in as test user</button>;
}

​
Parameters

​
projectId
string
required
Your Replyke project ID.
​
privateKey
string
required
Your project’s private key, used to sign the JWT. This key is available in your Replyke dashboard. Never expose this in production code.
​
userData
object
required
The user data to encode in the JWT payload. Must include id (the external user’s identifier). Additional fields are passed through as custom claims.
{
  id: string;           // Required: external user identifier
  [key: string]: any;   // Optional: name, email, avatar, etc.
}

​
Returns

Returns Promise<string | undefined>. On success, resolves to a signed JWT string that can be passed to the external auth sign-in flow.

​
Notes

  • The function logs a console warning each time it is called as a reminder that it is not for production use.
  • Use the returned token with the external authentication flow described in External Authentication.