The addition of "ROMs" to the term suggests a focus on unauthorized copies. In the PS4 modding scene, the files in question are almost always . These are retail game packages that have been decrypted, modified, and then "fake signed" with leaked development keys, replacing the official license check with a fake one that allows the game to run without PSN authentication.
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Partly. Emulators exist but are far from perfect. Most playable games are 2D indie titles. Heavy 3D games (God of War, Spider-Man) struggle or crash. Real PS4 hardware + jailbreak is still the main way. The addition of "ROMs" to the term suggests