Fuwa

Fuwa keeps a window visible while you work in other apps. Press Option-Command-P on the window you want, and the pinned picture follows that window as it moves and resizes, so you can still click the content underneath. A separate reference window can show only a chosen part of the screen, which suits a chat, a video or a document you need to keep in view.

It needs macOS 14 or later and runs on Apple silicon and Intel. The first pin asks for Screen Recording permission, and the README says window images are handled on the Mac. The DMG is not notarized and is signed with a local development certificate, so the first launch has to be allowed in System Settings. The README is in Chinese, with English and other translations in its docs folder.