Why Google changes page titles in SERP?

I just discovered why this is so!

Google displays the so-called snippet in the SERP (search engine results pages) differently depending on the screen width (desktop and mobile). This means that the length of the snippet can vary. It's not enough to say that for desktop it's 66 characters (and it's not 66) because Google takes into account the width of each character, measuring it in pixels.

The most important thing I discovered is that if the title of your home page is short enough, Google will add that shorter title to every title that has enough space to display fully with that addition!

Here is an example from my experience:

The title of the home page was:

Programming and Website Development - Dejan's Web

Google was adding the first part of that title to the mobile version in the following way:

News, articles, guides, programming functions, and more - Dejan's Web - Programming and Website Development

This is because Google reserves and displays more characters for the mobile version than for the desktop.

To optimize page titles for display in the SERP, I recommend paying attention to the length of the title and the width of the characters. This way, you can ensure that your titles are displayed in full and attract user attention, regardless of the device they are using.