Two spaces between sentences is an old habit still practiced by many writers today

I started writing on a typewriter. The rule was: Put two spaces between sentences. I did that with relish for many years and it became second nature. On a typewriter it had special appeal because I could hear each tap on the space bar reverberate across the room as the carriage clunked ahead. The practice also produced a precise cadence to the writing, by adding bravado to the end of each sentence. After all, two spaces was much more final than one, or, perish the thought, none.

Many years later when I came back to writing after being away building houses and chasing bugs on finely manicured lawns, I was using a computer. The editor of a print magazine admonished me to only use one space between sentences, and so that became the new norm for me. I very quickly learned to like it because the tactile response of a computer keyboard was smooth and quiet, and the absence of a carriage meant there was no audible reward for the extra space. 

Here’s a sentence with two spaces after it.  Today, it seems almost excessive, and it screams waste. But others, and there is a dividing line as rigid on this as on any contentious political issue today, say two spaces enliven the page with more white, and more white helps to break up the daunting task of reading. To some others in academia and the legal profession the extra space is a necessity.

Of the six sources I checked all agreed that one space is correct. The 2020 “Associated Press Stylebook” uses one space between sentencesMost also agreed the two space rule originated with typewriters since they rendered letters non-proportionately – they all took up the same amount of space. Our modern computer fonts, it is claimed, manage the space proportionately so the extra space between sentences isn’t needed. 

Regardless of the quirks of typefaces and computer fonts, if you use one space after a sentence you will be in good company, and if being right is important, you will have plenty of evidence to back you up.