In PowerPoint Online, you can insert an online video from YouTube or Vimeo on a slide.
Insert an online video
In your web browser, locate the video you want.
Copy the URL of the web page from the Address bar of your browser.
Switch to PowerPoint Online and select the slide where you want to place the video.
On the Insert tab of the ribbon, in the Media group, select Online Video.
In the Online Video dialog box, paste the URL you copied in step 2.
The video is inserted on your slide. You can move the video by dragging with the mouse, and you can resize the video frame by selecting a corner and dragging.
To play the video, you must run Slide Show. On the ribbon, switch to the View tab, and in the Start Slide Show group, select From Current Slide.
Slide Show opens, and then you can click the play button to begin.
For related information, see Play a video in PowerPoint Online.