By default browsers let us select the text in the browser using the keyboard, pressing the cmd-A combination on a Mac for example, or using the mouse.

How can you disable that, to make your web page behave more like an app and less like a document?

Use the user-select: none; CSS rule.

You need to use browser prefixes, as https://caniuse.com/#feat=user-select-none tells us:

-webkit-touch-callout: none;
  -webkit-user-select: none;
   -khtml-user-select: none;
     -moz-user-select: none;
      -ms-user-select: none;
          user-select: none;

One thing I use sometimes is to make all the app interface unselectable applying user-select: none; on the body element, then I can re-enable it on specific elements, using:

user-select: text;

Lessons in this unit:

0:	Introduction
1:	How to center an element with CSS
2:	CSS Border inside the element
3:	What are good CSS Breakpoint values for Responsive Design?
4:	How to debug CSS by bisecting
5:	▶︎ How to disable text selection using CSS
6:	How to put an item at the bottom of its container using CSS
7:	CSS, how to select elements that do NOT have a class
8:	How to stick an element on the bottom of the page with flexbox
9:	How to apply padding to multiple lines in CSS
10:	Making a table responsive using CSS
11:	CSS url()
12:	How to make an element smaller or bigger with CSS
13:	Customizing visited links
14:	Fix extra space after inline element
15:	How to create a sidebar that’s sticky but also scrolls
16:	How to embed YouTube videos using the correct aspect ratio
17:	Responsive pre tags in CSS
18:	Responsive YouTube Video Embeds
19:	How to remove all CSS from a page at once
20:	How I added Dark Mode to my website
21:	How to add a simple dark mode