This quickstart uses X-Unsafe-API-Key which is not safe for production.

See the nextjs-ts example for a more robust example.

​
TL;DR

1

Steal this code

Save the following code locally as index.html.
2

Open in browser

Open index.html in your browser.
3

Add API key

Add your Ultravox API key.
4

Start call

Click the button.
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Ultravox Web Quickstart</title>
  <script src="https://cdn.tailwindcss.com"></script>
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.4.0/css/all.min.css">
</head>
<body class="bg-gray-100 min-h-screen py-8">
  <div class="max-w-4xl mx-auto px-4">
    <div class="bg-white rounded-lg shadow-lg p-6">
      <!-- WARNING: DO NOT USE IN PRODUCTION -->
      <div class="bg-yellow-50 border-l-4 border-yellow-400 p-4 mb-6">
        <div class="flex">
          <div class="flex-shrink-0 fas fa-exclamation-triangle text-yellow-400"></div>
          <div class="ml-3">
            <h3 class="text-sm text-yellow-800">DEVELOPMENT ONLY - DO NOT USE IN PRODUCTION</h3>
            <p class="mt-1 text-sm text-yellow-700">This interface exposes API keys in client-side code and uses unsafe headers to bypass CORS.</p>
            <p class="mt-1 text-sm text-yellow-700">For a robust example, see the <a href="https://github.com/fixie-ai/ultravox-examples/tree/main/web/nextjs-ts">nextjs-ts</a> example.</p>
          </div>
        </div>
      </div>
      <form class="space-y-6">
        <div class="bg-gray-50 rounded-lg p-4">
          <h3 class="text-sm text-gray-900 mb-2">Call Status</h3>
          <div id="callStatus" class="text-sm text-gray-600">Ready</div>
        </div>
        <div>
          <label for="apiKey" class="block text-sm text-gray-700 mb-2">Ultravox API Key:</label>
          <input type="password" id="apiKey" 
            class="w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-blue-500"
            placeholder="Enter your Ultravox API key">
          <p class="mt-1 text-sm text-gray-500">Your API key will be used to create the call. Keep this secure!</p>
        </div>
        <div>
          <label for="systemPrompt" class="block text-sm text-gray-700 mb-2">System Prompt:</label>
          <textarea id="systemPrompt" rows="3" 
            class="w-full px-3 py-2 border border-gray-300 rounded-md shadow-sm focus:outline-none focus:ring-2 focus:ring-blue-500 focus:border-blue-500"
            placeholder="Enter system prompt for the AI assistant">You are a helpful assistant.</textarea>
          <p class="mt-1 text-sm text-gray-500">This prompt will define how the AI assistant behaves during the call.</p>
        </div>
        <div class="flex space-x-3">
          <button type="button" id="startCall"
            class="inline-flex items-center px-4 py-2 border border-transparent text-sm rounded-md shadow-sm text-white bg-green-600 hover:bg-green-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-green-500 transition-colors">
            Start Call
          </button>
          <button type="button" id="endCall"
            class="inline-flex items-center px-4 py-2 border border-transparent text-sm rounded-md shadow-sm text-white bg-red-600 hover:bg-red-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-red-500 transition-colors">
            End Call
          </button>
        </div>
      </form>
    </div>
  </div>
  <script type="module">
    import { UltravoxSession } from 'https://esm.sh/ultravox-client@0.3.6';
    
    let uvSession = new UltravoxSession();
    
    function appendUpdate(target, message) {
        const updateTarget = document.getElementById(target);
        if(target === 'callTranscript') {
            let transcriptText = '';
            message.map((transcript, index) => (
                transcriptText += '<div class="p-2 bg-gray-50 rounded border-l-4 border-blue-400"><span class="font-semibold text-gray-800">' + transcript.speaker + ':</span> <span class="text-gray-700">' + transcript.text + '</span></div>'
            ));
            updateTarget.innerHTML = transcriptText;
            updateTarget.scrollTop = updateTarget.scrollHeight;
        } else {
            updateTarget.innerHTML = message;
        }
    }
    
    // ⚠️ WARNING: DO NOT USE IN PRODUCTION! ⚠️
    // This function makes API calls directly from the client with API keys exposed
    // API keys should never be handled in client-side code in production
    // In production, API calls should be made from a secure server
    // Here we are using unsafe API endpoint to bypass CORS - this is a security risk
    async function createCall(apiKey, systemPrompt) {
      try {
        appendUpdate('callStatus', '<span class="text-blue-600">Creating call...</span>');
        
        const payload = {
          temperature: 0.3,
          systemPrompt: systemPrompt
        };
        
        console.log('Creating call with payload:', payload);
        
        // ⚠️ WARNING: X-Unsafe-API-Key header is used to bypass CORS ⚠️
        // This is NOT secure and should NEVER be used in production
        const response = await fetch('https://api.ultravox.ai/api/calls', {
          method: 'POST',
          headers: {
              'Content-Type': 'application/json',
              'X-Unsafe-API-Key': apiKey  // ⚠️ UNSAFE - DO NOT USE IN PROD ⚠️
          },
          body: JSON.stringify(payload)
        });
        
        if (!response.ok) {
          throw new Error(`HTTP error! status: ${response.status}`);
        }
        
        const callData = await response.json();
        console.log('Call created successfully:', callData);
        
        return callData.joinUrl;
          
      } catch (error) {
          console.error('Error creating call:', error);
          appendUpdate('callStatus', `<span class="text-red-600">Error creating call: ${error.message}</span>`);
          throw error;
      }
    }
    
    // Start Call button click event handler
    document.getElementById('startCall').onclick = async function() {
      const apiKey = document.getElementById('apiKey').value;
      const systemPrompt = document.getElementById('systemPrompt').value || 'You are a helpful assistant.';
      
      if (!apiKey) {
        appendUpdate('callStatus', '<span class="text-red-600">Please enter your Ultravox API key</span>');
        return;
      }
      
      try {
        const joinUrl = await createCall(apiKey, systemPrompt);
        
        if (!joinUrl) {
          appendUpdate('callStatus', '<span class="text-red-600">Failed to get join URL from API</span>');
          return;
        }
        
        appendUpdate('callStatus', '<span class="text-blue-600">Joining call...</span>');
        
        uvSession.addEventListener('status', (event) => {
          let statusClass = 'text-blue-600';
          if (uvSession.status === 'connected') statusClass = 'text-green-600';
          if (uvSession.status === 'disconnected') statusClass = 'text-gray-600';
          appendUpdate('callStatus', `<span class="${statusClass}">Session status: ${uvSession.status}</span>`);
        });
        
        uvSession.joinCall(joinUrl);
          
      } catch (error) {
          appendUpdate('callStatus', `<span class="text-red-600">Failed to start call: ${error.message}</span>`);
      }
    };
    
    // End Call button click event handler
    document.getElementById('endCall').onclick = async function() {
      appendUpdate('callStatus', '<span class="text-yellow-600">Ending call...</span>');
      uvSession.leaveCall();
    };
  </script>
</body>
</html>

​
Next Steps

  1. Check out the nextjs-ts example for a more complete, production ready web app.