refern's own site lists all three — Windows, macOS and Linux — as supported platforms, with no version held back for one over the others. One $35 licence covers up to three of your own devices, in any mix of those operating systems, so a Mac and a Windows laptop can share the same licence.
Why this is the question to ask before the price
For anyone working on a single Mac and nothing else, platform breadth is not the feature that decides a purchase — Coii Ref only runs on macOS and costs $19 less for exactly that narrower scope. It matters the moment a second machine is a different operating system: a studio with a mix of Windows and Mac workstations, or one person who switches between a desktop and a Linux machine, has a real reason to pick the app that covers all three rather than pay twice or stay on one tool per platform.
~/Pictures/Reference- Concept boards
- Reference pulls
- coii-thumbnailswritten by Coii Ref
- coii-proxieswritten by Coii Ref
- coii.dbwritten by Coii Ref
What running on three platforms actually requires
Supporting Windows, macOS and Linux from one codebase is a real engineering commitment, not a checkbox — file-watching, window chrome and even basic things like keyboard shortcuts behave differently enough across the three that "it compiles everywhere" and "it feels native everywhere" are not the same claim. refern's own site treats all three as first-class rather than listing two platforms plus a compatibility layer for the third, which is worth noticing if cross-platform reach is specifically what you are paying for, since not every app that claims three platforms built them to the same standard.
What the Mac-only alternative buys back
Coii Ref trades the other two platforms away and narrows the rest of the app along with them: no on-device tagger, no search by meaning, no browser extension, no relationship graph. What it keeps is a smaller, cheaper app built for exactly one operating system, with nothing in the interface hedging for a platform it does not run on — no settings pane for a feature that only exists on Windows, no keyboard shortcut that means something different on Linux. The full comparison walks through the rest of that trade, row by row, rather than platform alone.
Neither decision is the "correct" one in general. A studio running Macs exclusively gains nothing from paying for Windows and Linux support it will never exercise, and a freelancer who switches between a Mac at home and a Windows machine at a client's office gains real flexibility from paying for exactly that.
Worth deciding before either purchase: if you are certain you will only ever touch a Mac, platform breadth is a feature you are paying for and never using, which is a reasonable thing to want to avoid on principle even before the price comes into it.
If you are choosing specifically because you are on a Mac and only a Mac, the built-for page covers what a Mac-native reference manager looks like applied to a real folder of images. If refern's reach across three platforms is the deciding feature, what else people weigh against it covers the rest of the field for comparison. Or try Coii Ref — thirty days, no card, no account.