What Is OpenEmu: How to Play Retro Games on Your Modern Mac

As companies move away from older consoles and new operating systems render many games unplayable, it becomes harder to play all your favorite games from the past. Game conservation has never been more important, but the industry as a whole has mostly failed here. 

Valiant efforts have been made by the Internet Archive and GOG.com to preserve classic arcade, console, and computer games, but the major game developers could be doing more. As nice as it is to have subscriptions to Xbox Game Pass, PlayStation Plus, or Nintendo Switch Online, those services can be shut off at any time.

There are a number of ways to enjoy the old console games you grew up playing—including building your own machine or buying a retro console—but the most accessible is the emulator, a program that lets you play any game in any operating system.

Unfortunately, the web is now littered with dozens of programs promising different results, and not all ROMs are compatible with current operating systems. What's worse—all the focus seems centered on emulating games with your Windows PC, but what if you have a Mac? Don't despair: OpenEmu is the perfect solution for retro gamers who only have access to macOS. If you have a Mac and fond memories of game consoles past, read on.

What Is OpenEmu?

Released in 2013, OpenEmu is not actually an emulator. Instead, it's a robust front end for other console emulators. On its own, that's nothing new; front ends have existed for a long time. OpenEmu differentiates itself by working a lot like a streamlined iTunes—that is, if iTunes were smooth and fast, not sluggish, confusing, and dead.

For example, OpenEmu has a built-in library that shows you box art for each of your games, and automatically sorts by platform. It also lets you make custom collections across multiple platforms and universalizes controller schemes for each emulated system. It all comes wrapped in an easy-to-understand and attractive interface.

The best part is that OpenEmu provides the emulators for each platform right out of the box. When you download the program, it already comes packaged with a large selection of emulators, or integrated cores. You don't have to hunt down the right core that is compatible with the ROM you have. Some systems also have multiple cores included, so there's never an issue with incompatibility. 

What Consoles Does OpenEmu Support?

OpenEmu has the ability to play games from a large collection of home consoles. Supported systems include the Atari 2600, Super NES, Sega Genesis, Game Boy, Sony PlayStation, Nintendo 64, Nintendo GameCube, Sony PSP, and more. For a full list, see the table below:

In theory, OpenEmu is also compatible with some arcade ROMs, but support is experimental and your success getting these games to run may vary. In general, MAME ROMs are the only type that can be played inside OpenEmu. If you come across JAMMA or Neo Geo games in your search, they won't work. 

Games for home computers from the '70s and '80s are not supported—you'll need separate emulators for, say, the Atari 800 or 1040ST. Also, more complex older systems like the Dreamcast, PlayStation 2, and Xbox are not supported either.

How to Play Games on OpenEmu

Step 1: Install OpenEmu

Head to OpenEmu.org and click Experimental under the Download Now button. This might sound dangerous, but it just means you'll have extended platform compatibility and some features that are still in development, such as support for arcade games.

(Credit: OpenEmu)

Step 2: Allow the App

When you try to launch OpenEmu after downloading it, your Mac probably won't let you because the developer is unverified. To fix this, you can follow Apple's instructions. Locate the downloaded OpenEmu file in Finder and Control-click on the app icon. Select Open from the shortcut menu, then click Open to make an exception to the OS' security settings. The app will then be added to your Applications folder.

(Credit: PCMag / Apple)

Step 3: Finalize Setup

When you launch the app for the first time, OpenEmu will take you through a very short setup process where you can select which cores you want to download. You can just leave these options selected by default, since there's no reason not to get every core available. Click Next, then Go to finally launch OpenEmu.

(Credit: PCMag / OpenEmu)

Step 4: Download ROM Files

OpenEmu can play games out of the box, but it doesn't come with any games included. In order to start playing retro games, you'll have to download them separately.

Take note that owning ROMs is generally considered to be a legal gray area, since they are derived from a given company's intellectual property. In reality, just don't try to make money off them—like Nintendo Switch emulator Yuzu did—and you'll be fine.

Though we can't directly link to any ROM sites, they're pretty easy to find. Most sites are reputable but use your best judgment when downloading files from the internet, and run them through an anti-malware app to be safe.

(Credit: PCMag / OpenEmu)

Step 5: Unzip Your ROMs

When you download a ROM file, they typically come zipped inside a zip or 7-zip file. The built-in Archive Utility on your Mac should be able to open these files, but if you're looking for something more powerful, you can download The Unarchiver. If it's a MAME ROM, leave the file zipped.

Once the file is unzipped, you should have the ROM file. It usually has a file extension named after the system it's for, so NES games are .nes files, Game Boy Color games are .gbc files, etc. Bigger games can also be a .ISO file. Sometimes you might also find a few supporting text files included with the ROM, but you won't need them for playing.

(Credit: MacPaw)

Step 6: Add ROMs to Your Library

Add the ROM to OpenEmu by dragging the individual file (not the folder) directly into the interface's main window. The program almost always knows where to put the file, but if it's in the wrong place, you can drag it to the appropriate folder. For MAME files, dump the entire zipped folder into the Arcade section of OpenEmu. Since this is still an experimental feature, support can be buggy. It may show up in the wrong folder, or do something else wonky.

When a ROM is added, OpenEmu will search the web for box art, but if it can't find any, use Google Image Search to locate your own. There's no downloading required—you can find an image (.JPEG or .PNG file) and drag it directly onto the empty space where the box art should be.

Note that game files are added to ~/Library/Application Support/OpenEmu/Game Library by default. However, you can change this under OpenEmu > Preferences > Library.

(Credit: PCMag / OpenEmu)

Step 7: Connect a Controller

OpenEmu allows you to play any game using your Mac's keyboard, but why would you want to? The program is compatible with any HID-compliant USB or Bluetooth game controller, so you might as well pull out your favorite gamepad when you're ready to start playing.

Put your preferred controller into pairing mode and open your Mac's Bluetooth settings menu. Select the controller from the list of devices to establish the connection. OpenEmu has a long list of supported controllers.

(Credit: 8Bitdo)

Step 8: Customize the Controller Setup

OpenEmu should be able to automatically map your controls, but you can customize input from OpenEmu > Preferences > Controls. Use the drop-down menu to choose a system. Game input is mapped to your keyboard, but you can open the Input drop-down menu and choose your controller. Button assignments can then be changed for individual consoles.

Each action has a field next to it that you can change to your preference. Directional input can be mapped to a joystick or D-pad. Special functions like quick save, mute, pause, and screenshot can also be mapped to any button. You can even add rewind and fast forward buttons, if you want to make old school games just a little more forgiving.

(Credit: PCMag / OpenEmu)

Step 9: Start Playing

To get playing, first choose a console from the left side of the OpenEmu library, then double-click on the box art of your game of choice. Despite taking place on your Mac screen, you should find that gameplay is just like you remember it.

If you find the controls need further adjustment, hit the gear icon on the OpenEmu toolbar and click Edit Game Controls to tweak the controller scheme. The game should accept these new controls on the fly, without needing to restart.

Done playing for the day? Save your progress on the Save States page. OpenEmu can even auto-save for you and preserve several different save states. Want to take a screenshot? Hit Command + T (or your re-assigned button) to save the screen in the Screenshots page of the program.

(Credit: PCMag / OpenEmu)

Extra: Add Screen Filters

This one is not strictly necessary, but it becomes screamingly obvious on a modern monitor how low-res all of these games were if you don't add a screen filter. To apply one, head to OpenEmu > Preferences > Gameplay and open the Shader drop-down menu.

Play around with what you like best—the CRT and VCR filters, for instance, make games look like you're playing on an old TV screen with scan lines and everything. Just make sure to close and reopen the game so the new styles can be implemented.

Extra: Add BIOS Files For Certain Consoles

One major complication when playing retro games is that some systems, such as the original PlayStation and Sega Saturn, require BIOS files to work. These special ROM files emulate the operating system of the console. OpenEmu has a user guide on BIOS files, but it's not too complicated that you can't figure it out yourself.

The good news is that OpenEmu is smart enough to know what's missing. If you run into this issue, a message will appear on the screen to tell you exactly what files you need to download. From there, it's just a matter of hunting down the right files and getting them into the system.

For PlayStation games, you will need several BIOS files: scph5500.bin, scph5501.bin, and scph5502.bin. If you can't find the last one, but have found scph5552.bin, you can simply rename it to match the necessary file name. Sega Saturn games need: sega_101.bin and mpr-17933.bin. Some console add-ons like the Sega CD, Sega 32X, and the TurboGrafx-CD are supported, but may also be a little finicky.

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Instead of adding these BIOS files into OpenEmu like a game ROM, you will have to drag them into the ~/Library/Application Support/OpenEmu/BIOS folder directly. Go to OpenEmu > Preferences > System Files to see which cores require additional BIOS files to work. You will also be able to see which ones you have added and which you still need.

Remember to Clean Up Your Library

Keep in mind that OpenEmu doesn't just move a ROM's location, it actually duplicates the file itself—one version in your Application Support files and another will continue to exist in your downloads folder (or wherever you have it saved).

This is important only because you should probably keep an eye on how much you're downloading. While most 8- and 16-bit game ROMs only take up a few kilobytes or megabytes of room, files for more modern system will begin to take up hundreds of megabytes or even several gigabytes. Some games can even require you to download multiple discs to get the whole game.

Having duplicate files around can lead to storage crunch, so you can safely delete the file you originally downloaded once you confirm the game works in OpenEmu. 

Want to Avoid ROMs Altogether? Try Homebrew Titles

If you don't feel like messing with ROMS at all, OpenEmu actually includes a decent number of custom-built games called Homebrews. These titles are built by hobbyists to run on proprietary hardware, resulting in games that look and feel like classic console installments but are actually modern inventions. 

Open the program's main menu and select the Homebrew tab to view the list of games available. You'll find fan-made titles like Halo 2600 for the Atari 2600, an SNES remake of the Donkey Kong arcade game called Classic Kong, and a compilation of several Pac-Man titles called Pac-Man Collection for the Atari 7800.