Should you put one forward space or two after a period?
It all depends on whether you’re adept at typography—and whether you’re willing to move on from something you might have learned years ago in a typewriting class.
Here’s what you’ll find in The Redbook: A Manual on Legal Style (5th ed. 2023): “Although it’s true that 19th-century typesetters put a bit more space between sentences than between words within a sentence, it has been a settled convention for many decades in professional typesetting to put only one space between sentences. Many who learned to put two spaces in typewriting classes still cling to that practice, but the enlightened approach is to shed it.” (P. 101.)
And here’s what the spanking-new Chicago Manual of Style (18th ed. 2024) says: “Chicago advises leaving a single character space, not two spaces, between sentences and after colons used within a sentence . . . [A] well-structured electronic document will never include more than one consecutive character space.” (P. 69.)
So it’s entirely up to you.