Q: Keynote: Play video on iPad and External Monitor synchroniously

Hello jp.kalus.

Thank you for using the Apple Support Communities. I understand you would like to display a Keynote presentation from your iPad on a external display. There are a couple of options to achieve this. 

Our first option would be to use the AirPlay Mirroring feature in your iPad, so you can display your iPad's screen on to an Apple TV connected to an external display via HDMI. Here's an knowledge base article with more info:

How to use AirPlay on your iPhone, iPad, or iPod touch

Our other option is to use an Apple Lightning Digital AV Adapter to connect the iPad to the external display via HDMI cable. Here's an article with more info about our adapters, and the link to the Apple Lightning Digital AV Adapter page in the Apple Online Store:

About Apple Digital AV Adapters for iPhone, iPad, and iPod touch

iPhone Accessories - Lightning Digital AV Adapter

Regards.

Hey jp.kalus,

You can add video to a slide in Keynote. When you show the slide during a presentation, the video starts playing when you tap, or you can set the video to start automatically when the slide appears. And you can mirror it to an external display with the steps shared above by stuckboss. Here's an article with more details:

Keynote for iPad: Add video and audio

Have a great day.