Frequently Asked Questions

Do you upload my ROM or patch to a server?

No. Patching runs locally in your browser. Your ROM and patch files stay on your device. Your browser may only download the final patched file when you click apply.

Do you store any personal data or file contents?

RomPatcher.app does not need your ROM/patch contents to work. If analytics are used, they should be limited to basic site metrics (page views) and not your files. See Privacy Policy for details.

Is it legal to patch ROMs?

Only use ROMs you legally own and patches you have permission to use. RomPatcher.app does not host or distribute ROMs or copyrighted game files.

Is RomPatcher.app safe to use?

Patching runs in your browser and doesn’t require installing software. For maximum safety, use patches from trusted creators, avoid unknown “mod packs,” and keep your browser up to date.

Which patch formats are supported?

Common formats include IPS, BPS, UPS, PPF, and XDELTA/VCDIFF (plus any extra formats included in the RomPatcher.js build). If a patch isn’t recognized, try Auto-detect or see Patch Formats.

Should I choose a patch type or use Auto-detect?

Auto-detect is recommended for most users. Choose a patch type only if you know the exact format or want the file picker filtered to specific extensions.

My patch is a ZIP file — what do I do?

Some creators bundle multiple patches in a ZIP (different regions, optional add-ons). If your build supports ZIP patches, select the ZIP and choose the correct patch inside (if prompted). Otherwise, extract the ZIP and select the patch file directly.

My patch is .7z or .rar — can I use it here?

Usually you need to extract .7z or .rar first, then upload the actual patch file inside (like .ips, .bps, .ups, .xdelta).

Can I apply multiple patches to the same ROM?

Sometimes, but only if the creator specifically supports it (e.g., “base patch” + “optional add-on”). Apply in the exact order the patch author recommends. Random patch stacking often breaks things.

Why does my patch fail to apply?

The most common reason is a base ROM mismatch (wrong region/revision, header difference, or a different dump). Use a clean ROM that matches the patch notes. If the author lists a hash (MD5/SHA1), match it exactly.

What does “base ROM required” mean?

A patch is not a full game. It’s a set of changes that must be applied to a specific original game file. Example: a patch may require Pokémon Emerald (USA) and will fail on Pokémon Emerald (EU) or a different revision.

What are CRC/MD5/SHA1 hashes and why do they matter?

Hashes are “fingerprints” of a file. Patch authors often list a required hash so you can confirm your base ROM is exactly the expected one. If your hash doesn’t match, the patch may fail or produce a broken game.

What’s the difference between region and revision?

• Region is the release territory (USA, Europe, Japan, etc.).
• Revision is an updated release of the same region (often labeled v1.0, v1.1, Rev A, etc.).

A patch may require a specific region and revision, not just “the same game title.”

My ROM size looks different (trimmed) — will that break patches?

It can. Some formats tolerate trimming, others don’t—especially strict formats like XDELTA. If patching fails, use an untrimmed clean dump that matches the author’s hash/checksum.

What does “headered/unheadered ROM” mean?

Some older ROM images contain an extra header (metadata) at the start of the file. If a patch was made for a headered ROM and you use an unheadered ROM (or vice versa), patching can fail or the output can be corrupted. Always follow the patch readme.

XDELTA/VCDIFF patch fails — what should I check?

XDELTA is very strict. Even tiny differences in the base file (revision/region, trimmed file, different dump) will fail. Confirm the exact base file and hashes listed by the patch author. If your patch came with a “source file name,” match that too.

The patch applied, but the game crashes / black screens. Why?

Common causes:

• Wrong base ROM (patch “applied” but output is invalid)
• Wrong emulator/core settings
• Patch requires expansion or special mapper support
• You applied add-ons in the wrong order

Re-check the base ROM hash and the patch instructions.

Will my save file work with the patched ROM?

Sometimes. Minor patches usually keep saves compatible, but big hacks can change save structure and break compatibility. If the hack has its own save type, start a fresh save unless the creator says your original save is supported.

Where does the patched ROM go after I apply the patch?

The patched ROM downloads to your browser’s default download location (usually your Downloads folder). Your files are not uploaded anywhere.

The output file has a weird name or extension — is that normal?

Sometimes browsers rename downloads. If your emulator needs a specific extension (like .gba, .nes, .sfc), you can safely rename the file extension—just don’t change the file contents.

Does patching change my original ROM file?

No. The tool creates a new patched output. Your original ROM file remains unchanged on your device.

I’m on iPhone/iPad — why can’t I select some files?

Mobile browsers can have limitations with large files or file picker filtering. If selection fails, try Auto-detect, use the Files app to pick the ROM/patch, or use a desktop browser for very large patches.

Android says “permission denied” or I can’t see my files — what now?

Use the system file picker (not a third-party file manager), and ensure the browser has storage access. If it still fails, move files to the “Downloads” folder and try again.

Patching is slow or crashes — what can I do?

Large files and XDELTA patches can be heavy in the browser. Close other tabs, try a desktop browser, and ensure enough free memory. If available, use a smaller patch format provided by the author (e.g., BPS instead of XDELTA).

Does private/incognito mode affect patching?

It can. Some browsers restrict downloads or storage in private mode. If you have download issues, try normal mode.

I’m not sure which file is the patch and which is the base ROM — how do I tell?

The base ROM is the original game file (often ends in .gba, .nes, .sfc, etc.). The patch is usually a smaller file ending in .ips, .bps, .ups, .ppf, or .xdelta. Patch downloads often include a readme that says exactly which base ROM is required.

Can I patch an already patched ROM?

Usually no. Most patches expect a clean base ROM. If you want to apply a different patch, start again from the clean original ROM.

Is this only for Pokémon? Can I patch other games too?

It works for any game as long as you have a compatible base file and a supported patch format. Pokémon hacks are common, but the tool isn’t limited to any one series.

“Unknown patch format” or “Not supported” — what does it mean?

Your patch file may be compressed (ZIP/7Z/RAR), renamed, or it’s a format not included in the current build. Extract archives first and try Auto-detect. If it still fails, the patch format may not be supported on this site build.

Could my patch download be corrupted?

Yes. If patching fails unexpectedly, re-download the patch from the original source and try again. If the author provides a checksum for the patch file itself, verify it.

I still can’t patch — how do I get help?

Check the patch readme for the required base ROM + hashes. If you need help, contact us and include:

• Patch file name + format (IPS/BPS/UPS/XDELTA/etc.)
• Base ROM game + region + revision (if known)
• Any error message shown on the page
• Your browser + device (Chrome/Firefox/Safari, desktop/mobile)