How to prefetch video? I'm baffled and annoyed by Blender's playback speed. From searching the internet for the past hour or so, I've gathered you can somehow prefetch the video (I'm using the video sequencer) to make it faster. However for the love of me I can't find this option. I'm using the latest version of blender (2.80). I've read that pressing 'P'should do it but that just highlights my mouse with dotted lines.

How can I change my preferences so that blender will always prefetch the video?
You'll find it in the Preview sidebar:

Shortcut 'P' is for setting the preview range, and will not influence the playback speed.
If you do not want to mess with proxies(which is the natural next step), try lowering the resolution percentage:

Nb. make sure that the project resolution is set to match your footage, by selecting a movie strip and in the menu select Movie Strip &gt; Set render size.