Jazz Jackrabbit 2 for Mac and Linux

Jazz Jackrabbit 2 now runs natively on Mac and Linux, and on the Steam Deck. It isn't Wine, an emulator or a remake. These builds are made from the Windows game's own code, so it plays exactly as it does on Windows: single player, split screen and online, and you can host or join games with people on the Windows version.

Where they came from
At the end of October we started decompiling JJ2 1.24, The Secret Files: turning the Windows Jazz2.exe back into C, one function at a time. Each of the game's 1,098 functions was checked against the original running in the game, and the last one went in six days after we started. As a final check, the ten demos that come with the game play back on our code exactly as they do on the original, frame for frame.

With the whole game rebuilt, the only parts left to replace were the ones that talk to Windows: the window, graphics, sound, input and networking. The first Mac build played online with Windows players on 4 November, and the Linux build followed two days later.

What's new
The game still runs at its original 70 updates a second, so it plays the same. What's changed is how you see it:

• Bigger views: up to 1920x1080 instead of 640x480, so you see more of the level. Zoom in or out to suit.
• Smooth motion: a new frame is drawn at every refresh of your display, so it's smooth at 60 Hz, 120 Hz or anything else.
• Split screen: up to four players, each with a bigger view than before.
• Picture styles: Sharp Pixels, Soft, Smooth Edges and Arcade CRT, with optional scanlines.
• Settings over the game: change any of it mid-game, with the keyboard or a controller. Xbox, PlayStation and Switch Pro controllers all work.

For online games there's a setting called Competitive Online, on by default, which keeps your view to 800x600 at most so a big screen doesn't let you see further than anyone else.

What you need

• Your own copy of JJ2 1.24. The GOG release works. The game's files aren't included.
• Mac: Apple silicon (M1 or later) and macOS 13 or newer.
• Linux: any 64-bit Linux with Flatpak. SteamOS already has it, and the download page explains how to start it from the Steam Deck's Game Mode.

The Mac app isn't signed with an Apple developer ID, so macOS blocks it the first time you open it. The download page shows how to get past that, and you only have to do it once.

Not yet: JJ2+
These are builds of plain 1.24, so they can't join Plus Only servers yet. Levels made for the original game play as normal and plenty of JJ2+ levels load, but ones that need JJ2+ itself show the same error the Windows version does without it. JJ2+ support is what we're working on now: online play on JJ2+ servers first, then levels with scripts, then the HUD, menus and chat commands. It will come out as one release once all of it works and has been play-tested.

Why the source isn't public
Only to stop quick cheats turning up in competitive online games. It isn't closed for good, and others will decompile the game in time anyway. If you're active in a community project, whether that's JJ2+, Jazz² Resurrection or something else, get in touch and we'll share the code and the test harness.

Thanks
djazz is lead tester for the Linux build, and I've done the Mac testing. Thanks also to Xtreem and SlazRabbit. The decompiling itself was done by Claude and Codex, two AI coding agents, against a test harness that compares every function with the original game. This couldn't have been done any other way.

If the game crashes it saves a report. Please post it here with a note of what you were doing. The full story, with all the figures, is on the JJ2 Decomp Project page.

Download Jazz Jackrabbit 2 for Mac and Linux
Build 1.3.3​