Screenshots large and blurry on retina displays

If you edit a card, click on Cards, and then place the following at the very bottom of the styling section, it will shrink screenshots down to the correct size:

img { zoom: 50%; }

The problem is that it will shrink all images by 50%. Images from high resolution displays will now look correct, but images you obtain from other sources may now look too small.

Unfortunately there is no good solution to this problem at the moment - the web technologies Anki uses do not have a way of detecting which images need to be resized. Resizing the images prior to adding them to Anki will allow you to mix and match other images, but it requires some setup:

If you're on Windows, an Anki user suggested using SnagIt as a workaround: