Title tag content length based on character pixel width

Question

I read that the length of the contents in a title tag depends on the character pixel width. What does this mean?

I'm referring to an article that I read on Search Engine Land:

http://searchengineland.com/definitive-seo-audit-part-2-3-content-site-252492

The visible title tag length has changed over time but is currently 70 to 71 characters, up from roughly 50 to 60 depending on the character pixel width.

Does this relate to desktops or mobile devices?

How do you work out pixel width? Is there a set length for different devices?

Answer 1

It's the pixel length on Google.

This applies to both platforms, they're moving towards a material card design that has been turning up on Google.com for users assigned to the test group. This would function identically on both platforms. Google has made it clear they consider Mobile the primary platform and Desktop secondary. For this reason, all future design decisions are based on a mobile first design philosophy.

You can preview this by using Chrome developer console (F12) to just change the text on your current result. If it shoots over the pixel limit, Google's design will shorten it and append '...' to indicate missing content. The same goes for the description lines.