Screengrab is more worth while
An anon split it into three parts over the weekend.
Mac:
Press and hold these three keys together: Shift, Command and 4. to select the area of the screen to capture. To move the selection, press and hold Space bar while dragging. To cancel taking the screenshot, press the Esc (Escape) key.
Windows:
Use built in snipping tool
To dl Twit vids:
https://twittervideodownloader.com/