Have you ever noticed that the small images on Github are actually characters instead of traditional image files? Let's take the small person image that is used when assigning someone to an issue as an example. When you hover over the small person image, your cursor changes to the text cursor. If you inspect element, you'll see that the styling of the span includes content: "" . By removing this line, the image disappears. It seems like Github's small images are all made up of "characters". This could be a reason why their website loads quickly since they don't have to load these assets.
How do they go about creating these "character images"?