Hit Ctrl + F8 to capture a static PNG image.
Hit Ctrl + F9 to start capturing a GIF video, and hit the same key combination again to end the capture. Once the capture ends, it takes some time to process the capture and generate the final file.
Hit Ctrl + F10 to start capturing a WEBM video, and hit the same key combination again to end the capture. WEBM videos are processed instantly.
In all three cases, the browser downloads the resulting file and makes it available in the downloads folder.