Embedding quickstart

This walks through the shortest path to a working embed: generate a token from your backend, render the iframe, and see a connection. It assumes you have a published widget and an API key.

Before you start

You'll need:

• An API key — From Settings → API Keys. Use a fsk_test_ key while developing. See Authentication & API Keys.

• Your org identifier (endOrgId) — The internal UUID for the customer the widget is for. See Finding Your Org Identifier.

• A backend — Any server environment where you can make an HTTP request with a secret API key.

Step 1: Generate a token from your backend

Create a server-side function that calls the Fastn token endpoint. Keep the API key in an environment variable — never in client code.

// Server-side only
async function getFastnToken({ userEmail, userName }) {
  const res = await fetch("https://api.fastn.dev/api/v1/embed/token", {
    method: "POST",
    headers: {
      "Authorization": `Bearer ${process.env.FASTN_API_KEY}`,
      "Content-Type": "application/json",
      // Required only for fsk_test_ keys:
      "X-fastn-Test-Mode": "true",
    },
    body: JSON.stringify({
      endOrgId: process.env.FASTN_END_ORG_ID,
      userEmail,
      userName,
    }),
  });

  const json = await res.json();
  // The token is nested under `data`
  return json.data.token;
}

Note: the response nests the token under data — read json.data.token, not json.token.

Step 2: Expose the token to your frontend

Create an endpoint your frontend can call to get a fresh token. Return only the token, never the API key.

// Example route
app.get("/api/fastn-token", async (req, res) => {
  const token = await getFastnToken({
    userEmail: req.user.email,
    userName: req.user.name,
  });
  res.json({ token });
});

Step 3: Render the iframe

On your frontend, fetch a token and render the Fastn iframe with it.

const { token } = await fetch("/api/fastn-token").then(r => r.json());

const iframe = document.createElement("iframe");
// Org-level (shared) embed — see the Tenancy guide for user-level
iframe.src = `https://api.fastn.dev/api/v1/embed/iframe?token=${token}`;
iframe.style.width = "100%";
iframe.style.height = "100%";
iframe.style.border = "none";
document.getElementById("integrations").appendChild(iframe);

Step 4: Verify

Load the page. The Fastn widget should render inside your application. You should see the integrations you added to the widget, each with a Connect button.

Click Connect on one, complete the authentication popup, and confirm the app shows as Connected.

If the iframe is blank

The most common cause is an expired or hardcoded token. Confirm your frontend fetches a fresh token on each load rather than reusing one. See Troubleshooting.