MenubarX

It is a Mac menu bar application that allows you to pin browser windows as if they were small apps.

You can use it for free with feature limitations since it is a paid application. This app is also included in the Setapp subscription.

You can create up to 2 icons/tabs in the menu bar in the free version, and unlimited in the full version.

The windows can be resized, pinned, kept on top, or placed in floating mode.

Additionally, you can interact with the window’s content just like you do with a browser window, allowing you to use web tools and/or services directly from the macOS menu bar.

It allows you to set the user-agent for each window. You can also enjoy notifications in each window.

It’s an app that delivers on its promises, it’s lightweight since it barely consumes resources, and quite simple to use yet highly customizable. It’s a shame the free version only allows 2 tabs, but it’s more than enough for most cases.