>>41499212Press the Capture button for a screenshot.
Hold it to record the last 30 seconds of gameplay as a video.
The record function isn't available in some games (Smash being the biggest example) but has been usable in most games released since it was added. It's supported in Pokemon Sword and Shield.
Webm related, I made it by just recording it, posting it through twitter from the Switch itself, saving the video from twitter and converting it to webm.
