Q. Should I use one or two spaces after a period?

APA 6th Edition

A manual directs authors to use two spaces after a period (American Psychological Association, 2010, p. 88). However, as per a March 18th, 2014 tweet from @APA_Style, which is the official twitter account for the Publication Manual of the American Psychological Association (6th ed.), authors can use one or two spaces:

The tweet reflects what I've heard from most RRU instructors, which is that they aren't particularly concerned whether students use one or two spaces as long as the spacing is consistent. Accordingly, unless an editor or instructor has directed you specifically to use one or two spaces after closing punctuation, please use the approach that works best for you and be consistent. 

References

American Psychological Association [APA_Style]. (2014, March 18). @FMCatalano @craigbeebe @StacyLOliver APA allows either 1 or 2 spaces after a period; just be consistent. Everybody's happy [Tweet]. Retrieved from https://twitter.com/APA_Style/status/446010271002558464

American Psychological Association. (2010). Publication manual of the American Psychological Association (6th ed.). Washington, DC: Author.

APA 7th Edition

The APA manual directs authors to use one space after a period (American Psychological Association, 2020, p. 154). Unless an editor or instructor has directed you specifically to use  two spaces after closing punctuation, please insert a single space after end punctuation marks in sentences, such as periods, question marks, or exclamation marks.

Reference

American Psychological Association. (2020). Publication manual of the American Psychological Association (7th ed.). https://doi.org/10.1037/0000165-000