Browser Calling

Browser Calling

Let a user place a call straight from your web app, no phone required. Browser calling is a two-step handshake: mint a WebRTC session on the server, register it in the browser, then dial. The split exists so you never bridge a call to a browser that has not finished registering.

1. Mint a session (server)

Call createVoiceWebSession (POST /v1/voice/calls/web) from your backend. It returns a short-lived token and a credentialId the browser needs.

const { data } = await zernio.voice.createVoiceWebSession({});
// Send data.token + data.credentialId to the browser
// (the number to dial from is chosen later, at the /web/dial step)

curl -X POST "https://zernio.com/api/v1/voice/calls/web" \
  -H "Authorization: Bearer YOUR_API_KEY"

2. Register in the browser

Register the token with the @telnyx/webrtc SDK. Once the client reports it is registered, you are ready to dial.

import { TelnyxRTC } from '@telnyx/webrtc';

const client = new TelnyxRTC({ login_token: token });
client.on('telnyx.ready', () => {
  // registered and ready to place a call
});
client.connect();

3. Dial

With the client registered, call dialVoiceWebCall (POST /v1/voice/calls/web/dial) with the credentialId from step 1 to place the call. Pass fromNumber (E.164, optional) to choose which of your numbers to dial from; omit it if you only have one.

curl -X POST "https://zernio.com/api/v1/voice/calls/web/dial" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"credentialId": "CREDENTIAL_ID", "to": "+13105551234", "fromNumber": "+14155550100"}'

The call then behaves like any other: it shows up in history and honors the number's recording and transcription settings.