What Improvement Patches Are — How They Differ from Translations and How to Apply Them

About 4 min read · 2026-11-07

When people talk about retro game patches they usually mean translations. But many patches leave the text alone and change the game itself: they fix bugs in the original, smooth out slowdown, make the controls more comfortable or swap the music for higher-quality audio. This site collects those separately as improvement patches.

This guide covers the kinds of improvement patches, what they share with translation patches, and what to be careful about when using the two together.

What they have in common with translations

They are made and applied the same way. The original ROM stays untouched and a small file recording only the changes is distributed for you to lay over your own copy. They use the same IPS, BPS, PPF and xdelta formats, so applying one works exactly as described in How to Apply a Translation Patch.

They also target a specific original. An improvement patch is built against one region and revision of a ROM; applied to another, it is either rejected or breaks the game. See Picking the right ROM for how to check yours.

Kinds of improvement patches

• Bug fixes — fix errors in the original that block progress, make items vanish or corrupt the screen under certain conditions; problems that could not be fixed once the cartridge shipped
• Slowdown reduction — reduce the stretches where the game slows down or sprites flicker when many enemies appear. Some work as if the game ran on a faster chip and need an emulator or device that supports it
• Controls and quality of life — remap buttons, put a dash on a single button, speed up text and similar tweaks
• Enhanced music — patches such as MSU-1 on the Super Famicom or MD+ on the Mega Drive play CD-quality music instead of the original chip tunes. Besides the ROM patch they need separate audio files, and you only hear them on a flash cart or emulator that supports the format
• Undoing regional changes — restore elements that were changed or removed in an overseas release, or bring over the strengths of another region's version

What each patch changes differs from patch to patch, so read the description and version history on its page first.

Combining with a translation patch

The most common question is whether you can apply both a translation and an improvement patch. In short: not by simply stacking them.

A patch file is a list of "change byte N to this". Those positions are based on the original the patch was made from. A ROM that already has a translation applied no longer matches that original, so laying an improvement patch made for the original on top can overwrite the wrong places and break the game. Formats that check the target, such as BPS and xdelta, refuse to apply at all.

To use both, one of these has to be true:

1. A combined patch — the author built the translation and the improvement into one patch. This site sometimes lists these separately, e.g. "Korean & MD+ patch". This is the safest option
2. A stated order — the author says something like "apply this to a ROM that already has the translation". Then follow the stated order and target exactly

If the description says neither, don't stack them; pick one.

Applying on this site

Drop the original (or a zip containing it) onto Apply online on any improvement patch page and the patch is applied right there. Nothing is uploaded; it all happens in your browser.

Some games list more than one patch, for example one for the Japanese release and one for the North American release. The moment you drop the original, its CRC32 is read and the matching patch is selected for you. If nothing matches you are told the original differs; compare your file with the target ROM details on the patch page, and use the file inspector to check its hashes.

If you have the patch file yourself, dropping it onto the ROM patch tool together with the original gives the same result.

After applying

• Keep the original separately. The patched file is saved under a new name, but to try another patch you always start again from an untouched original
• Saves may not carry over. If a patch changes the save layout, old saves may not load or may corrupt. Copy important saves first
• Check your emulator's automatic patching. Some emulators automatically apply a same-named .ips sitting next to the ROM. Tidy these up so an already patched ROM isn't patched twice
• On real hardware, check device support. Patches that add enhanced audio or chip features behave differently depending on the flash cart

Summary

Improvement patches are made and applied exactly like translation patches; only what they change is different. When combining one with a translation, use a combined patch or follow the order the author gives, and always keep an untouched original.

We do not provide game ROMs. Patches are distributed on the assumption that you apply them to a backup of a game you legitimately own.