In the sphinx book theme I was doing a bit of research on good practices for design around web content for readability and accessibility. One thing that I consistently ran into was that you should shoot for 45-75 characters per line, with a max of 80 characters. (though note that Wikipedia seemed to think that a longer width was OK for material that needs to be information dense and "scannable"). They also consistently recommended 16px as the font base size.

Currently, our base font size is 15px, and the max width allows for about 108 characters per line on my screen.

What do people think about these two changes to this theme:

• Set the font base size to 16px to be a bit larger. Here's one ref that recommends this.
• Set the main content max-width such that, at a 16px font size, we have ~90 characters per line. (this is more than the recommended line width, but IMO this is OK since documentation content may have the same "scannability" needs that wikipedia does...I am happy to hear countering opinions on this one!).

What do folks think about this? (cc also @bollwyvl whose perspective on accessibility I have appreciated!)

Some refs:

• Best practices for line width and accessibility and this criterion page from W3C as well
• Visual design guide from accessibility.digital.gov
• wikipedia page discussing their intent to cap the line width
• the Tufte CSS page
  • a max-width of 1400px for all content, and then sets 55% for the main text and 45% for the sidebar text.
  • Main content: 55% of full width. Roughly 85 characters per line. Font size 1.4rem
  • Margin content: 50% of width of the main content. Roughly 60 characters per line. Font size 1.1rem
• webtypography recommends about 66 characters per line