Google regularly introduces new features in Chrome through 'flags,' toggles that are only accessible through the chrome://flags page. Even though the flags page is hidden, Google also sometimes enables experimental features automatically in limited tests, leaving some to wonder what changed. Now it seems Google is working on a more obvious place to try unfinished features.
Google tries out a lot of tweaks on its early Chrome browser and Chrome OS builds, though most of it isn't immediately user-facing. In the Chrome 91 build some of those changes will be more obvious thanks to the Experiments menu, previously called Labs. You can find it by clicking the beaker icon that's now next to your user icon in the menu bar, and it's now enabled by default on Canary.