You may never have noticed but basically every meme uses the same font to write on a picture. Phil Edwards took a look at why:

• The font is called “Impact” and was created in 1965 with hand cut metal letters.
• Because it had thick letters it was known for its legibility, even when it was superimposed onto pictures.
• The font was sold to a company that then licensed it to Microsoft which made it a default font in its Windows products, massively increasing its distribution.
• Then Impact had its threshold moment when it was used in the genre defining meme: the “I Can Has Cheezburger” cat meme.
• Now it has become so associated with memes that any that don’t use the font just won’t look right.

Read more about the history of the font (or strictly speaking, typeface), chart its rise in old brochures and iconic memes, and other details here.

Source: Vox