build-zoom-video-sdk-app

What this skill does

# /build-zoom-video-sdk-app

Background reference for fully custom video-session products. Prefer `plan-zoom-product` first when the boundary between Meeting SDK and Video SDK is still unclear.

Build custom video experiences powered by Zoom's infrastructure.

## Hard Routing Guardrail (Read First)

- If the user asks for custom real-time video app behavior (topic/session join, custom rendering, attach/detach), route to Video SDK.
- Do not switch to REST meeting endpoints for Video SDK join flows.
- Video SDK does not use Meeting IDs, `join_url`, or Meeting SDK join payload fields (`meetingNumber`, `passWord`).

## Meeting SDK vs Video SDK

| Feature | Meeting SDK | Video SDK |
|---------|-------------|-----------|
| UI | Default Zoom UI or Custom UI | **Fully custom UI** (you build it) |
| Experience | Zoom meetings | Video sessions |
| Branding | Limited customization | **Full branding control** |
| Features | Full Zoom features | Core video features |

## UI Options (Web)

Video SDK gives you **full control over the UI**:

| Option | Description |
|--------|-------------|
| **UI Toolkit** | Pre-built React components (low-code) |
| **Custom UI** | Build your own UI using the SDK APIs |

## Prerequisites

- Zoom Video SDK credentials from Marketplace
- SDK Key and Secret
- Web development environment

> **Need help with OAuth or signatures?** See the **[zoom-oauth](../oauth/SKILL.md)** skill for authentication flows.

> **Need pre-join diagnostics on web?** Use **[probe-sdk](../probe-sdk/SKILL.md)** before Video SDK `join()` to reduce first-minute failures.

> **Start troubleshooting fast:** Use the **[5-Minute Runbook](RUNBOOK.md)** before deep debugging.

## Quick Start (Web)

### NPM Usage (Bundler like Vite/Webpack)

```javascript
import ZoomVideo from '@zoom/videosdk';

const client = ZoomVideo.createClient();
await client.init('en-US', 'Global', { patchJsMedia: true });
await client.join(topic, signature, userName, password);

// IMPORTANT: getMediaStream() ONLY works AFTER join()
const stream = client.getMediaStream();
await stream.startVideo();
await stream.startAudio();
```

### CDN Usage (No Bundler)

> **WARNING: Ad blockers block `source.zoom.us`**. Self-host the SDK to avoid issues.

```bash
# Download SDK locally
curl "https://source.zoom.us/videosdk/zoom-video-1.12.0.min.js" -o js/zoom-video-sdk.min.js
```

```html
<script src="js/zoom-video-sdk.min.js"></script>
```

```javascript
// CDN exports as WebVideoSDK, NOT ZoomVideo
// Must use .default property
const ZoomVideo = WebVideoSDK.default;
const client = ZoomVideo.createClient();

await client.init('en-US', 'Global', { patchJsMedia: true });
await client.join(topic, signature, userName, password);

// IMPORTANT: getMediaStream() ONLY works AFTER join()
const stream = client.getMediaStream();
await stream.startVideo();
await stream.startAudio();
```

### ES Module with CDN (Race Condition Fix)

When using `<script type="module">` with CDN, SDK may not be loaded yet:

```javascript
// Wait for SDK to load before using
function waitForSDK(timeout = 10000) {
  return new Promise((resolve, reject) => {
    if (typeof WebVideoSDK !== 'undefined') {
      resolve();
      return;
    }
    const start = Date.now();
    const check = setInterval(() => {
      if (typeof WebVideoSDK !== 'undefined') {
        clearInterval(check);
        resolve();
      } else if (Date.now() - start > timeout) {
        clearInterval(check);
        reject(new Error('SDK failed to load'));
      }
    }, 100);
  });
}

// Usage
await waitForSDK();
const ZoomVideo = WebVideoSDK.default;
const client = ZoomVideo.createClient();
```

## SDK Lifecycle (CRITICAL ORDER)

The SDK has a strict lifecycle. Violating it causes silent failures.

```
1. Create client:     client = ZoomVideo.createClient()
2. Initialize:        await client.init('en-US', 'Global', options)
3. Join session:      await client.join(topic, signature, userName, password)
4. Get stream:        stream = client.getMediaStream()  ← ONLY AFTER JOIN
5. Start media:       await stream.startVideo() / await stream.startAudio()
```

**Common Mistake (Silent Failure):**

```javascript
// ❌ WRONG: Getting stream before joining
const client = ZoomVideo.createClient();
await client.init('en-US', 'Global');
const stream = client.getMediaStream();  // Returns undefined!
await client.join(...);

// ✅ CORRECT: Get stream after joining
const client = ZoomVideo.createClient();
await client.init('en-US', 'Global');
await client.join(...);
const stream = client.getMediaStream();  // Works!
```

## Video Rendering (Event-Driven)

**The SDK is event-driven.** You must listen for events and render videos accordingly.

### Use `attachVideo()` NOT `renderVideo()`

```javascript
import { VideoQuality } from '@zoom/videosdk';

// Start your camera
await stream.startVideo();

// Attach video - returns element to append to DOM
const element = await stream.attachVideo(userId, VideoQuality.Video_360P);
container.appendChild(element);

// Detach when done
await stream.detachVideo(userId);
```

### Required Events

```javascript
// When other participant's video turns on/off
client.on('peer-video-state-change', async (payload) => {
  const { action, userId } = payload;
  if (action === 'Start') {
    const el = await stream.attachVideo(userId, VideoQuality.Video_360P);
    container.appendChild(el);
  } else {
    await stream.detachVideo(userId);
  }
});

// When participants join/leave
client.on('user-added', (payload) => { /* check bVideoOn */ });
client.on('user-removed', (payload) => { stream.detachVideo(payload.userId); });
```

See [web/references/web.md](web/references/web.md) for complete event handling patterns.

## Key Concepts

| Concept | Description |
|---------|-------------|
| Session | Video session (not a meeting) |
| Topic | Session identifier (any string you choose) |
| Signature | JWT for authorization |
| MediaStream | Audio/video stream control |

## Session Creation Model

**Important**: Video SDK sessions are created **just-in-time**, not in advance.

| Aspect | Video SDK | Meeting SDK |
|--------|-----------|-------------|
| Pre-creation | NOT required | Create meeting via API first |
| Session start | First participant joins with topic | Join existing meeting ID |
| Topic | Any string (you define it) | Meeting ID from API |
| Scheduling | N/A - sessions are ad-hoc | Meetings can be scheduled |

### How Sessions Work

1. **No pre-creation needed**: Sessions don't exist until someone joins
2. **Topic = Session ID**: Any participants joining with the same `topic` string join the same session
3. **First join creates it**: The session is created when the first participant joins
4. **No meeting ID**: There's no numeric meeting ID like in Zoom Meetings

```javascript
// Session is created on-the-fly when first user joins
// Any string can be the topic - it becomes the session identifier
await client.join('my-custom-session-123', signature, 'User Name');

// Other participants join the SAME session by using the SAME topic
await client.join('my-custom-session-123', signature, 'Another User');
```

### Signature Endpoint Setup

The signature endpoint must be accessible from your frontend without CORS issues.

**Option 1: Same-Origin Proxy (Recommended)**

```nginx
# Nginx config
location /api/ {
    proxy_pass http://YOUR_BACKEND_HOST:3005/api/;
    proxy_http_version 1.1;
    proxy_set_header Host $host;
}
```

```javascript
// Frontend uses relative URL (same origin)
const response = await fetch('/api/signature', { ... });
```

**Option 2: CORS Configuration**

```javascript
// Express.js backend
const cors = require('cors');
app.use(cors({
  origin: ['https://your-domain.com'],
  credentials: true
}));
```

**WARNING:** Mixed content (HTTPS page → HTTP API) will be blocked by browsers.

## Use Cases

| Use Case | Description |
|----------|-------------|
| [Video SDK BYOS (Bring Your Own Storage)](../general/use-cases/video-sdk-bring-your-own-storage.