---
"@context": https://schema.org
"@type": TechArticle
"@id": https://www.twilio.com/docs/video/specifying-video-constraints#article
headline: Specify Video Constraints for Javascript v2.x
description: Sample code and instructions that show how to set constraints on a Programmable Video LocalVideoTrack for optimization.
url: https://www.twilio.com/docs/video/specifying-video-constraints
inLanguage: en
dateModified: 2026-03-09T18:47:22.000Z
author:
  "@type": Organization
  name: Twilio Developer Education Team
publisher:
  "@type": Organization
  name: Twilio
---

# Specify Video Constraints for Javascript v2.x

You can customize the video capture by setting [video constraints](https://developer.mozilla.org/en-US/docs/Web/API/MediaTrackConstraints#Properties_of_video_tracks) on a LocalVideoTrack. Setting constraints, lets you optimize the video track to network and device conditions. You can set size constraints, frame rate constraints or the aspect ratio constraints of your choice. Note that video constraints are used to resolve the capture format, but the actual video sent to Participant may be downscaled temporally or spatially in response to network and device conditions.

```js
const { connect, createLocalTracks } = require('twilio-video');

// Option 1
createLocalTracks({
  audio: true,
  video: { width: 640 },
}).then(localTracks => {
  return connect('$TOKEN', {
    name: 'my-room-name',
    tracks: localTracks,
  });
}).then(room => {
  console.log(`Connected to Room: ${room.name}`);
});

// Option 2
connect('$TOKEN', {
  audio: true,
  name: 'my-room-name',
  video: { width: 640 },
}).then(room => {
  console.log(`Connected to Room: ${room.name}`);
});
```