Putting two spaces after a period is one of the more annoying things I encounter when I’m editing. This typographical sin is usually committed by people in particular demographics, often those who were around when typewriters were still in use or those who witnessed the rise of the personal computer and the word processor.

The thing is, our technology has evolved. We don’t need to add two spaces after a period any longer.

Two Spaces after a Period: A Relic of a Past Era

Some people hit the space bar twice after they finish typing a sentence. In modern word processors, this results in two spaces after your period. You need to tap once in order to get the space after the period. If you don’t, Word or Pages or whatever program you happen to be using will tell you you’ve got a spelling error, as the final word of the previous sentence and the first word of the next are run together—that is, all the characters (including the period) are flush up against one another.

This can be tricky to see on the page. Editors and proofreaders will notice it relatively quickly. If you want to see for yourself, you can always turn on “invisibles”—the characters in word processors that show you where your spaces are, where soft breaks are, and where hard breaks are. (Pro tip: If you’re editing, always turn your invisibles on. I don’t work without them.)

Things weren’t always this way. Once upon a time, you had to hit the space key not once but twice in order to put the correct amount of space between a period and the next letter. Typewriters tended to use monospaced fonts, which have the same amount of horizontal space between every character. Periods sometimes got lost, so the convention of putting two spaces in was established.

The PC Revolution

The need to put two spaces in didn’t evaporate with the advent of the personal computer and the word processor. In fact, the QWERTY keyboard is modeled after the typewriter, and most word processors mimicked typewriter output in the early days. As programming became more sophisticated and the era of the manual typewriter faded into memory, typing itself has changed. For one thing, the keys of modern keyboards have a lot less resistance on them, making it much easier to push them. Touch-screens have further revolutionized our typing, predicting our next words and allowing us to drag-and-drop letters.

Word processors still operate much the same way typewriters did, however, so you still have to input the space after a period by yourself. Most of the first word-processing programs were rather unsophisticated, so not only were they not programmed to realize you needed a space after your period, they also didn’t have the “invisible” characters: spaces, hard returns, soft returns, and paragraph markers to show you where exactly your spaces were and what they looked like. Today, however, you can turn on invisibles and see exactly where your spaces and returns are.

What, then, of the second space after a period?

Two Wrongs Don’t Make a Right

There have long been hold outs in fields like psychology and the medical field. Even these fields have recently updated to adopt modern conventions. APA, MLA, and Chicago Manual of Style all recommend one space.

Given younger generations’ propensity to drop periods altogether, the double space seems to be going the way of the dinosaur, even in the most stodgy and traditional of fields.

There’s also the fact it’s wrong, no matter what some people seem to think.

I speak as someone who has worked with typesetters, proofreaders, and editors; and done some editing, proofreading, and typesetting myself. That second gap? Is incredibly noticeable on a typeset page. Every time I see one, it leaps up off the page.

What’s Wrong with It?

It’s just a second space, I hear you saying. What’s so bad about it? Well, it’s pointless for one thing.

Think about it. There is no other place where you’d put that emphatic double space. You wouldn’t put two spaces between words; it would look strange and gappy. Just as you wouldn’t put a space between the last word of the sentence and period, or a space between each letter of a word. So two spaces after a period one of those things that just makes no sense in terms of typography.

It’s extra work for the author, which, in turn, creates extra work for the editor, the proofreader, and the typesetter, who then have to set about stripping out all of those “extra” spaces. If you’re working on page proofs when that happens, each correction comes with an additional charge—and if you have put two spaces after every period, you’re going to run up the corrections bill removing them all. But they have to be taken out. Even APA recommends that one space should be used in publications.

I take two-spaced periods out with an automated tool that runs through Word. Nonetheless, some slip through. Some get by the copy editor. They end up in the proofs. And some of them, yes, even end up in a book or a journal. But they shouldn’t be there. Ever. Typesetters have no reason for them, so no one else should either. Contrary to that one flawed study, they don’t actually make reading faster or easier.

Why Did It Ever Become a Thing?

As mentioned, typewriters used monospaced fonts. Since all the letters take up the same amount of space, they tend to have a lot of space between them. That gives the text a much more open appearance. And in all that open space, it can be difficult to see where a tiny little period is. Adding the second space makes the end of a sentence much more apparent.

Modern word processors use proportional typefaces. Capital letters like “M” and “W” are a lot wider than other letters, so they take up more room. Given this, playing “spot the period” is a lot easier. There’s also a lot less space between letters on the whole, which means you’re not left guessing if the next letter is part of the same word or the next one.

In typesetting, the typesetter has much more freedom to play with the perceived space. We work with hairline spaces, something not available to those using a typewriter or even the average Word user today. We can increase the amount of space between characters by “a hair,” which often stops letters from bumping into each other. It can give them more room. A good example is writing “of World War II”: in some typefaces, with tighter kerning, the f and the W would touch. I would call for a hairspace to move them apart just enough that they didn’t touch.

The typewriter didn’t offer users this kind of nuance: It was either a space or no space. The solution is still to add more space, but typewriters didn’t have a “little bit of space” setting; you either added a whole en-space or nothing.

Just Use One Space after a Period

The thing is we don’t need to put two spaces after a period today. Word processors have evolved enough to compensate for this sort of thing. Word even has some fairly advanced settings for kerning and spacing, although it’s nowhere near as complex as you can get with typesetting programs.

Nonetheless, there’s little to no real reason to include a double space after your period. There’s no typographical argument, nor any sort of grammatical argument for including a second space.

So please, ditch two spaces after a period. Even Word now flags it, so it’s time to let this habit go the way of the dodo.