A free image editor that runs on Mac and Linux
Paint by Zaweba has a free Mac and Linux version that shares plugins and opens the same .ptx files as Windows, with some Windows-only parts left out.
Yes, a free image editor can run on a Mac or Linux, and Paint by Zaweba is one. Alongside the Windows version there's a Mac and Linux version that uses the same plugins and opens and saves the same .ptx files. Not every Windows feature is in it, and the MAC-LINUX.md file lists what's left out, but the core editor is there and it's free software like the Windows one.
That makes it possible to start a picture on a Windows desktop and finish it on a Mac laptop, or to use the same editor on a Linux workstation as on a family PC, without converting files or losing layers.
Why the same files matter
The .ptx format is Paint's own, where every layer, mask, adjustment layer and live effect stays editable. Because both versions read and write it, you're not stuck exporting a flattened PSD or TIFF to move between computers. Open the file on the other machine and it's exactly as you left it.
Plugins are shared too. Every tool in Paint is a plugin, so the tools you rely on behave the same on each system.
What to expect
Some parts of the Windows version depend on Windows itself. HEIC files, for example, are opened through the Windows codecs, and other features may rely on parts of Windows in the same way. Expect a few gaps like that, and check MAC-LINUX.md for the current list before you plan a job around a particular feature.
The best approach is to try your usual work on a sample file. If a tool you need is there, carry on; if not, do that step on Windows and the rest elsewhere, since the files move freely between them.
Getting started on a Mac or Linux
Install the Mac or Linux build, open a picture and work as you would on Windows. Keep your working files as .ptx so they stay fully editable across systems, and export JPEG, PNG or other formats only when you're finished.
If you share files with someone on another system, send the .ptx when they'll edit, and a JPEG or PNG when they only need to see the result.
Other free choices
There are other free editors on Mac and Linux, and some people use several. What sets Paint apart is the combination it brings from Windows: layers that stay editable, masks, adjustment layers, live Layer Art effects, a shared brush engine, RAW development, deep colour and CMYK documents, vector shapes and type, animation and batch automation, with no AI services, no telemetry and no account. On a Mac or Linux machine you get the same file format and plugins, so the way you work doesn't change.
A note on support
Paint by Zaweba was built on Windows first, and the Mac and Linux version followed. If you come across something that behaves differently, the Windows version is the reference. That doesn't stop the Mac and Linux version being useful every day; it just means the odd feature is Windows only.
Like the Windows version, it works offline and is free software under the EULA.
