QuickLookProtein is a macOS Quick Look extension to preview protein/3D structure files (PDB, SDF, CIF).
It works in all places where macOS uses Quick Look, e.g. in Finder and Spotlight. In Finder, just select the protein structure file and press Space to open Quick Look.
The rendering of the 3D structure is performed using 3Dmol.js.
The extension is packaged into a main app, whose purpose is to set a few settings used for the display of the 3D models. QuickLookProtein requires macOS Big Sur (version 11.0+).