You can download a Facebook video using an online video downloader such as All Video Downloader:1. Find the video you want to download on Facebook.2. Right-click on the video and select "Copy video URL" or "Copy link address."3. Open All Video Downloader, paste the video URL into the downloader's search bar, and click "Download" or "Go."4. Select the video quality and format you want to download, and the video will be saved to your device.