Two spaces between sentences is too many.
If you use Microsoft, you will now be met with those dreaded blue squiggly lines if you press the space bar twice after a period.
The change, first noticed by University of Denver law professor Alan Chen.
The one-spacers have won. Microsoft Word now showing 2 spaces after a period as an error.
— Alan Chen (@profalankchen) April 10, 2020
The habit of using two spaces is a relic from the era of typewriters, when typists spaced twice to more clearly define the end of a sentence.
Back in the days of typewriters, characters were “monopsaced,” meaning they took up the same amount of space on the page.
Today, most fonts adjust the width of characters so sentences are easier to read.