Is Three.js a good choice for a browser game?

It has been the default answer for 3D on the web for a decade and it still is. Expect to write more maths than an engine would ask of you, and expect the result to load in about a second.

How do you know these games were built with Three.js?

Makers pick their tools from a list when they submit, and that is what this page filters on. It is self-reported and nobody audits it, so treat it as a credit rather than a certificate. Where a game links its source, you can go and look.

Do I need Three.js to play these games?

No. Three.js is what the maker built with; the game ships as a page you open in a browser. Nothing on this list needs a plugin, a launcher or a download.

Where should I start if I want to build with Three.js?

Open the source link on any game here that has one, then read the official documentation at threejs.org. Reading one finished small game teaches more than a tutorial series, and a good number of makers on this site publish their repositories.

What kind of games do people make with Three.js?

Across the 545 games on this page, the most common categories are action, strategy and simulation. That is what makers actually shipped, counted from the listings themselves rather than estimated.