> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rime.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Build a voice agent (Node, no framework)
> Build a voice agent with Rime TTS in plain Node.js with zero dependencies: node:http and built-in fetch proxy synthesis server-side while the browser records speech and plays back Rime audio.
This guide builds a working voice agent with **zero dependencies** — no framework, no packages, no `npm install`. Just `node:http` and Node's built-in `fetch`. If you want the same agent on a framework, see the [Next.js](/docs/voice-agent-nextjs), [Vite](/docs/voice-agent-vite), [Express](/docs/voice-agent-express), or [FastAPI](/docs/voice-agent-fastapi) guides.
There is no Rime npm package — and you don't need one. Rime is a single HTTPS API.
```
Browser (mic + playback) → POST /api/tts (node:http) → POST https://users.rime.ai/v1/rime-tts
```
## Prerequisites
* A Rime API key from the [API Tokens page](https://app.rime.ai/tokens), exported as `RIME_API_KEY`
* Node.js 20.11 or later — nothing else
## 1. Server
Create `server.mjs`:
```javascript server.mjs theme={null}
import { createServer } from "node:http";
import { readFileSync } from "node:fs";
import path from "node:path";
const INDEX_HTML = readFileSync(path.join(import.meta.dirname, "index.html"));
async function handleTts(req, res) {
let body = "";
for await (const chunk of req) body += chunk;
let text, speaker, modelId;
try {
({ text, speaker = "astra", modelId = "coda" } = JSON.parse(body || "{}"));
} catch {
res.writeHead(400, { "Content-Type": "application/json" });
return res.end(JSON.stringify({ error: "invalid JSON body" }));
}
if (!text) {
res.writeHead(400, { "Content-Type": "application/json" });
return res.end(JSON.stringify({ error: "text is required" }));
}
const rimeRes = await fetch("https://users.rime.ai/v1/rime-tts", {
method: "POST",
headers: {
Authorization: `Bearer ${process.env.RIME_API_KEY}`,
"Content-Type": "application/json",
Accept: "audio/mpeg", // MP3; see the API reference for Opus, WAV, PCM, μ-law
},
body: JSON.stringify({ text, speaker, modelId }),
});
if (!rimeRes.ok) {
res.writeHead(rimeRes.status, { "Content-Type": "application/json" });
return res.end(
JSON.stringify({ error: `Rime API error ${rimeRes.status}`, detail: await rimeRes.text() }),
);
}
res.writeHead(200, { "Content-Type": "audio/mpeg" });
res.end(Buffer.from(await rimeRes.arrayBuffer()));
}
createServer(async (req, res) => {
if (req.method === "POST" && req.url === "/api/tts") return handleTts(req, res);
if (req.method === "GET" && req.url === "/") {
res.writeHead(200, { "Content-Type": "text/html" });
return res.end(INDEX_HTML);
}
res.writeHead(404, { "Content-Type": "application/json" });
res.end(JSON.stringify({ error: "not found" }));
}).listen(3000, () => console.log("Rime voice agent on http://localhost:3000"));
```
Verify it works before touching the frontend (create an empty `index.html` first if you're testing the API route alone):
```bash theme={null}
RIME_API_KEY=your_key node server.mjs &
curl -X POST http://localhost:3000/api/tts \
-H 'Content-Type: application/json' \
-d '{"text": "Hello from my plain Node voice agent."}' \
--output test.mp3
```
`test.mp3` should be playable audio. A 401 means `RIME_API_KEY` isn't visible to the server process.
## 2. Client: mic in, Rime audio out
Create `index.html` next to `server.mjs`. It uses the browser's built-in `SpeechRecognition` for input (Chrome/Edge/Safari), a stub `respond()` function as the agent brain, and your `/api/tts` route for the voice:
```html index.html theme={null}
Rime voice agent
Rime voice agent
```
Restart the server (it reads `index.html` at startup), open `http://localhost:3000`, click **Speak**, say something, and the agent answers in Rime's `astra` voice.
## Want streaming?
For incremental synthesis — audio starts playing while later sentences are still generating — connect your server to `wss://users-ws.rime.ai/ws3` and relay events to the browser. Rime's WebSocket endpoints authenticate with an `Authorization` header, which browser WebSockets cannot send, so the bridge always lives server-side; the browser-facing side needs the `ws` package (the one dependency streaming adds). The complete bridge implementation is in the [Next.js guide](/docs/voice-agent-nextjs#3-optional-stream-over-websockets) and works with this same `createServer` instance. The `/ws3` message schema is in the [Coda WebSocket reference](/api-reference/coda/websockets-json).
## Next steps
Endpoints, word-level timestamps, context IDs, and interruption handling.
Swap `astra` for any Coda voice across six languages.
Choose between Opus, MP3, WAV, PCM, and μ-law for your latency budget.
The core API walkthrough in cURL, Python, JavaScript, and TypeScript.