Docktor

About

Docktor is a Mac app for previewing app icons directly in the Dock, which is especially useful when you're designing or building Mac apps. Instead of guessing how an icon will look, you can see it in the actual Dock context. It requires macOS Sonoma or later.

Using it is simple: drag and drop a PNG onto the Docktor window or directly onto its icon in the Dock. If you add more than one image, you can scroll or use the arrow keys to quickly switch between them for comparison.

Docktor is available as a download from the website. There is no built-in payment feature; the developer suggests trying their other app, Hand Mirror, or sending a donation if you'd like to support the work.