Here's why Wii U emulator Cemu going open source is a big deal for emulation—and for the Steam Deck

Zelda Breath of the Wild key art
(Image credit: Nintendo)

On Tuesday, the creator of Wii U emulator Cemu announced a major 2.0 version release, introducing Linux builds for the first time and open sourcing eight years of work.

In 2017, Wii U emulator Cemu made history by pulling in thousands of dollars per month on Patreon to help fund development. Cemu's high profile Patreon, which was briefly earning $25,000 at its peak, raised questions about the ethics of emulation, particularly when money is involved, and when a project is "closed source" instead of open source, meaning their source code isn't publicly available. Closed source emulator development isn't inherently wrong, but it can be controversial—one of the key ways the emulation community protects itself from lawsuits is by keeping its source code public, so litigious companies like Nintendo can study it and confirm that none of its proprietary code is used in the reverse-engineering process.

Dolphin emulator developer Pierre Bourdon broke it down for me back in 2017. "You can save a lot of time if you ‘cheat’ and look at proprietary documentation (console SDKs, leaks, etc.) while trying to understand how a console works," he said. "This is in general frowned upon in many emulation projects: it puts the whole project at the risk of a lawsuit. It's one of the things where we have no doubts about the legality: it's clearly illegal. With open source projects the development process is usually very open."

Despite some worries in the community that Cemu would attract legal scrutiny thanks to its closed source code, lucrative Patreon and 4K Breath of the Wild videos, Nintendo never came knocking. And now worries that Cemu's source code could be lost if developer exzap ever disappeared are moot, too. The project in its entirety is available on Github, including Linux builds for the new 2.0 release.

Cemu's move to open source marks the end of the most prominent fan-made closed source emulator in existence. It's a great day for the continued preservation of Nintendo's games long into the future, considering the company's own emulation efforts are often disappointingly bad.

Exzap notes that the Linux support is "still very rough around the edges," but hopes that changes quickly as other emulator developers familiarize themselves with Cemu and begin to chip in on the project. Cemu previously only ran on Windows, but its Linux support now opens the door to easy installation on the Steam Deck, my favorite emulation system. It won't be easy to get going on the Deck until Cemu adds flatpak support for one-click installation, but that's already being discussed on the Github.

Cemu's creator used the 2.0 announcement to talk a bit about the emulator's history—they've been the sole developer for much of its run, and said that in the last couple years the project has been especially draining.

"Whenever I tell myself to make time for other things, I end up feeling guilty because my self-inflicted sense of responsibility drives me to always prioritize Cemu over my own interests. This year was especially intense because I single-handedly ported Cemu to Linux while also trying to deliver somewhat constant feature and bug fix updates," they wrote. "In the end, opening up development seems like the logical decision. It has always been the long-term plan anyway. With Cemu being open-source, the hope is that new contributors will pick up where I left off."

Exzap will still be contributing, but hopes having more developers will help with some significant features, like pausing and restarting emulation and improving performance on older hardware.

"I have been working on Cemu for almost 8 years now, watching the project grow from an experiment that seemed infeasible, to something that, at its peak, was used by more than a million people," exzap wrote on Tuesday. "Even today, when the Wii U has been mostly forgotten, we still get a quarter million downloads each month. There are still so many people enjoying Wii U games with Cemu and I will be eternally grateful that I got the chance to impact so many people's life in a positive way, even if just a tiny bit."

Wes Fenlon
Senior Editor

Wes has been covering games and hardware for more than 10 years, first at tech sites like The Wirecutter and Tested before joining the PC Gamer team in 2014. Wes plays a little bit of everything, but he'll always jump at the chance to cover emulation and Japanese games.

When he's not obsessively optimizing and re-optimizing a tangle of conveyor belts in Satisfactory (it's really becoming a problem), he's probably playing a 20-year-old Final Fantasy or some opaque ASCII roguelike. With a focus on writing and editing features, he seeks out personal stories and in-depth histories from the corners of PC gaming and its niche communities. 50% pizza by volume (deep dish, to be specific).