Typing double spaces after periods harkens back to the day of typewriters, when fonts were monospaced. All characters took up the same horizontal space on the page, resulting in excess white space between letters. It was difficult to see where sentences ended, but this problem was solved by adding a double space after periods.
Thanks to the invention of modern computers, double spaces are no longer necessary. Some “double-spacers”, however, argue against using a single space, making this a thorny issue amongst typographers.

Whoever lived here probably used double spaces.
Fortunately, when it comes to the use of spaces in your manuscript, there is no confusion. The Chicago Manual of Style, which is the style your copyeditor will use when editing your book, clearly calls for a single space. Good news, right?
Mostly right. If you’ve been using double spaces, you’ll need to do some clean up before sending your manuscript to your editor. Luckily, banishing double spaces is easy:
- Locate the control panel at the top of the page
- Click Edit, then Select All
- Click Edit, then Find, then Replace
- Tap the space bar twice with the cursor in the search field
- Tap the space bar once with the cursor in the replace field
- Click “Replace All”