Every modern typographer agrees on the one-space rule. It’s one of the canonical rules of the profession, in the same way that waiters know that the salad fork goes to the left of the dinner fork and fashion designers know to put men’s shirt buttons on the right and women’s on the left.
Above is an excerpt from an article featured in Slate written by Farhad Manjoo on why it is unequivocally wrong to use two spaces after a period, which just so happens to be a huge pet peeve of mine.
Manjoo discusses in the article how Typographers, The people who study and design the typewritten word, decided long ago that we should use one space, not two, between sentences. It’s been that way ever since, until one fateful day dawned: The day of the typewriter. Manjoo explains:
The problem with typewriters was that they used monospaced type—that is, every character occupied an equal amount of horizontal space. This bucked a long tradition of proportional typesetting, in which skinny characters (like I or 1) were given less space than fat ones (like W or M). Monospaced type gives you text that looks “loose” and uneven; there’s a lot of white space between characters and words, so it’s more difficult to spot the spaces between sentences immediately. Hence the adoption of the two-space rule—on a typewriter, an extra space after a sentence makes text easier to read. Here’s the thing, though: Monospaced fonts went out in the 1970s. First electric typewriters and then computers began to offer people ways to create text using proportional fonts. Today nearly every font on your PC is proportional. (Courier is the one major exception.) Because we’ve all switched to modern fonts, adding two spaces after a period no longer enhances readability, typographers say. It diminishes it.
So now you know why you’re not supposed to use two spaces after a period and you can avoid those uncomfortable moments and not look like a complete typographical ignoramus in front of your designer friends. You’re welcome.
Poster above by Craig Ward