I found this out first-hand when loading up my copy of Pokémon Gold—whether I’d caught ‘em all back in 2001, I’ll never be able to confirm, as the battery died at some point in the last quarter-century(!). Booting it up through the GB Operator was like switching it on for the first time. However, if it had still contained my surely-completed Pokédex, I’d have been able to copy that data to my laptop’s hard drive, replace the battery in the cartridge (a fiddly process, but doable), and then load the save back onto it—magic.
However, it’s worth noting that at present, everything relies on the cartridge’s actual save processes. While virtual “snapshot” saves—capturing a game at any given moment—are on Epilogue’s roadmap, the feature is not yet available. It will first be tested through the experimental “Nightly Builds” version of Playback (found at the bottom of the downloads page) before being fully implemented.
You can also use the GB Operator to dump the entire main game data from a cart you personally own, allowing you to make a legal copy for your own archival purposes (don’t share; that’s when it becomes piracy). The process itself is quick, depending on the game’s size, but even the Game Boy Advance’s biggest games were 32 MB at most. Even if you do back up a game in this manner, GB Operator still requires the original cart to run anything, though—you can’t just load the dumped ROM through the Playback software.
Finally, if you’re an aspiring developer or into retro-style indie games, it allows you to transfer homebrew games created through the likes of GB Studio onto a flash cart and play them on an actual Game Boy. It’s another niche feature, but one that’s great to have, allowing present-day creators to build on the legacy of the beloved handhelds.
It’s honestly hard to find much fault with the GB Operator. Even highlighting that it lacks real portability—sure, it’s tiny, but needing to be hooked up to a computer robs it of the pick-up-and-play appeal of the pocket-sized consoles it homages—feels like splitting hairs. It ultimately does everything it promises, all for less than $50.
This is a marvelous bit of kit, and the overall performance and utility bode extremely well for Epilogue’s upcoming SN Operator, which aims to do the same for the Super Nintendo as this does for the Game Boy family (and a mysterious “?? Operator” to follow). If you’re looking for an easy, low-budget way to revisit or revive your Game Boy collection, this is your best option.