Screenshots
Screenshots can be used to capture everything that is currently visible on the display of a smartphone, PC, etc. The image is saved on the device as a file.
How the picture can be taken, and where it is saved, always depend on the device and operating system. You can simply save screenshots, or put them in a document where you have already saved other information about the incident.
Instructions for different operating systems of computers as well as smartphones and tablets are available here:
You can find out how to create court-proof documentation of content on social media platforms at HateAid: legally watertight screenshots on social media.