Skip to main content
This guide walks you through setting up the backend server that generates temporary tokens for secure AssemblyAI WebSocket connections.

​
Environment Configuration

First, create an .env file in your project root to store your AssemblyAI API key securely:
.env
ASSEMBLYAI_API_KEY=YOUR_API_KEY
Never commit your .env file to version control. Add it to your .gitignore file to keep your API key secure.

​
Token Generation Function

The token generator creates temporary tokens that expire after a specified duration. This prevents exposing your permanent API key to the browser.
1

Create the token generator module

Create a tokenGenerator.js file that requests temporary tokens from AssemblyAI:
tokenGenerator.js
const axios = require('axios');
require("dotenv").config();

async function generateTempToken(expiresInSeconds) {
  const url = `https://streaming.assemblyai.com/v3/token?expires_in_seconds=${expiresInSeconds}`;

  try {
    const response = await axios.get(url, {
      headers: {
        Authorization: process.env.ASSEMBLYAI_API_KEY,
      },
    });
    return response.data.token;
  } catch (error) {
    console.error("Error generating temp token:", error.response?.data || error.message);
    throw error;
  }
}

module.exports = { generateTempToken };
Key points: Uses your permanent API key from environment variables, requests tokens with configurable expiration (max 600 seconds), and returns the temporary token string.
2

Set up the Express server

Create a server.js file that serves your frontend and provides the token endpoint:
server.js
const express = require("express");
const path = require("path");
const { generateTempToken } = require("./tokenGenerator");

const app = express();
const PORT = 8000;

// Serve static files from the public directory
app.use(express.static(path.join(__dirname, "public")));

// Token endpoint
app.get("/token", async (req, res) => {
  try {
    const token = await generateTempToken(60); // Token expires in 60 seconds
    res.json({ token });
  } catch (error) {
    res.status(500).json({ error: "Failed to generate token" });
  }
});

app.listen(PORT, () => {
  console.log(`Server is running at http://localhost:${PORT}`);
});
Server responsibilities: Serves static frontend files from the public/ directory (line 8), provides a /token endpoint that generates temporary tokens (lines 10-17), and returns tokens with 60-second expiration (maximum is 600 seconds).
3

Install dependencies

Install the required npm packages:
npm install express axios dotenv
4

Start the server

Run your server:
node server.js
You should see:
Server is running at http://localhost:8000

​
How It Works

The token flow ensures your API key never reaches the browser:
  1. Client requests token: Browser calls GET /token
  2. Server authenticates: Server uses permanent API key to request temporary token from AssemblyAI
  3. Token returned: Server sends temporary token to browser
  4. WebSocket connection: Browser uses temporary token to connect to AssemblyAI’s streaming endpoint
Temporary tokens are single-use and expire after the specified duration. This provides security while allowing client-side WebSocket connections.

​
Next Steps

With your server configured, you’re ready to:

Build docs developers (and LLMs) love

Get started for freeTalk to us