Why you should never, ever use two spaces after a period

He's amusingly wrong in his certainty that everybody else is wrong.

Two spaces grew out of a typographic convention of using a 1.5-width space that was favored by typesetters for proportional typespaces because typewriters didn't have half-width spaces represented on their keyboards. The actually "correct" approach would be 1.5-character width spaces, because even in proportional typefaces a little extra space serves as a useful visual cue that aids in quicker text scanning by eye.

The modern convention of using a single space is the result of journalistic publishers' desire for economy of printing paper. It costs more -- either money for extra pages or characters that won't fit on a page -- to have two (or even 1.5) spaces between sentences. For that reason, a new convention for non-personal correspondence arose, not out of "correctness" or readability concerns, but out of the miserliness of accountants.

As for the lack of studies, that's because it's pretty difficult to come up with a meaningful set of criteria that can be (relatively) easily measured in such a study. Worse, the people with both the resources and interest necessary to fund such studies are for the most part not interested in finding out their cost-saving measures make it harder to read their publications. People I know who read a lot -- who enjoy reading -- including myself all agree, though: having more than a single (proportional or otherwise) character width of space between sentences helps with making it easier to read quickly without having to backtrack and without missing things. In fact, if anything proportional typefaces makes the problem worse, because the spacing between sentences tends to end up smaller than it would otherwise be.

For all his annoying certainty that people who are certain of their disagreement with him are annoyingly wrong, Farhad Manjoo is pretty laughably lacking in the proud correctness he claims.

It seems that the reason it's wrong is that typographers say it is. The author has not given an actual reason, other than appeal to authority.

I will continue to double-space until I'm dead.

I'm a couple of years younger than Julian Assange and commonly use two spaces after each sentence, purely out of muscle memory. (I took a "keyboarding" class in 1987 or so using an IBM Selectric typewriter and that's the way I was taught to do it.)

I'm not at all surprised that many people still do this. I'm a little surprised that people assert that's a "proper" way to do it or for that matter get worked up enough about it to write that you should "never, ever" do it. Maybe it's the engineer in me, but I was expecting an actual negative consequence of using two spaces. Typography is important, but I'd guess that with modern kerning techniques the difference between two spaces and one is slight. (In fact, if I were designing a word processing app, I'd think this is is a case I'd account for: If there is a "proper" distance between the period at the end of one sentence and the start of the next letter, wouldn't you ensure that's the distance that is used whether the user typed one space or two?)

It seems to me, and Wikipedia seems to confirm, that single spaces after a period used to be called "French spacing" or "French bands". It was not standard US practice in the days of hot type or even photo type.

HN comments don't respect whitespace as typed when displaying them.

(' ' one space vs. ' ' two spaces)

An effect of HTML, I'm sure. When I edit the post, the 2 spaces between the second set of quotes is indeed still there.