“Be bold or italic, never regular” is a quote you’ll see now and then on the web. But when do you use a bold or italic font, and what about underlined text?

Many people have a hard time using these typographic emphasises consistently. In this article you’ll find a proposed set of rules.

Bold

To grab a viewer’s attention
To increase the contrast between headlines and body text
To highlight keywords

Italics

To highlight names (people, books, companies …)
To highlight Quotes
To highlight foreign words
To highlight a dialogue

Underlines

To highlight a hyperlink

Benefits

Increased reading speed
The content is more scannable
It improves the overall design of your blog post, website …

Recommendations

Use bold as little as possible! If everything is in a bold font, nothing will stand out.
Sans-serif italic faces don’t stand out much, consider using a bold font to make it stand out more. Most Sans-serif fonts have rather weak italics
A correct use of bold, underline and italic fonts can have a SEO benefit. However, do not overdo their use.
Don’t use underline in your body if it is not a hyperlink. It is too hard to see the difference between a hyperlink and underlined text.
Using bold for a whole paragraph makes it harder to read and can make the reader a bit nervous.
Semibold is often easier to read, but use bold if it should really stand out. In small text like body text, it is hard to notice semi bold.

And what about bold italics?

I couldn’t find really good use cases for bold italics, maybe it can be used on a poster or as an artistic choice to emphasize something. The use of a bold italic font will emphasize a bit too much in my opinion.

Interesting sources on web typography

A five minutes guide to better typography https://www.pierrickcalvez.com/journal/a-five-minutes-guide-to-better-typography
Professional Web Typography is a free ebook by Donny Truong
https://prowebtype.com/
A Pocket Guide to Master Every Day’s Typographic Adventures
http://www.typogui.de/

To sum it up

Do not overdo the use of bold and italic. Make sure what really matters stands out the most. A bold font will emphasize more than an italic font. Only use underline for hyperlinks.