What’s the number-one error I see in the content I edit? No, it’s not the misuse of there, their, or they’re. Nor is it the misuse of commas and apostrophes. This error makes me do a Find and Replace search before I even look at the first letter of the first word on the first page of a project. Give up? It’s the number of spaces after a period.
One space. Not two, not sometimes one but sometimes two and then sometimes five. One space.
I know, I just blew your mind and made you reconsider whether everything your English teachers taught you was a lie. But I speak the truth, and every major style guide backs me up on this.
In fact, the one-space rule has been part of the typesetting canon since the early 20th century. Why, then, does most of the public continue to believe that two spaces belong after a period? Because of the manual typewriter. It used a typeface that made it difficult to determine where one sentence ended and another began, so the two-space rule was born to help with readability. But that typeface isn’t used anymore, and, for the most part, neither are manual typewriters. Modern fonts and computers automatically account for the issues the two-space rule sought to address. Double spacing after a period is therefore obsolete.
That was the short of the long. If you want the long and a few more fun facts, read the article “Why You Should Never, Ever Put Two Spaces After a Period” from Business Insider.
And remember: use one space after a period. Always.