How to apply a ROM patch
To patch a ROM, open the patcher, select your original ROM file, select the patch file, then press Apply patch. The patched ROM downloads to your device. Everything runs inside your browser, so neither the ROM nor the patch is ever uploaded to a server.
What you need before you start
- The original ROM, unmodified. Patches are built against one exact file. A ROM you already patched will not work as a base.
- The patch file. Any of .ips, .bps, .ups, .aps, .rup, .ppf, .xdelta, .bdf, .ebp or .mod, or a zip containing one.
- A modern browser. Chrome, Firefox, Safari and Edge all work, on desktop and mobile.
Applying the patch, step by step
Open the patcher
Go to the ROM patcher. Nothing installs and nothing uploads.
Select your ROM
The checksums shown are your confirmation that the file is what you think it is.
Select the patch
Zip files are fine. If the archive holds several patches, pick from the list.
Review the header option
Only appears when a copier header is detected. See headers and zip files.
Press Apply patch
The patched ROM downloads. On a phone it goes to your Downloads folder.
How do you know the patch worked?
Formats that carry checksums, which means BPS, UPS, APS and RUP, verify the result themselves. If the patcher did not complain, the output matches what the author built.
For IPS, PPF and BSDiff there is nothing to verify against, because those formats store no checksum. If the hack author published a CRC32 for the patched ROM, check it with the checksum tool. Otherwise, load the ROM in an emulator and look at the title screen.
If it does not work
The overwhelming majority of failures come down to three things: the wrong ROM, a copier header mismatch, or an xdelta patch built with secondary compression. Each has a clear fix in fixing patch errors.
Frequently asked questions
Do my files get uploaded anywhere?
No. The patcher runs entirely in your browser using JavaScript and Web Workers. Your ROM and patch are read from disk into memory on your own device and never sent over the network. You can disconnect from the internet after the page loads and it still works.
Can I patch a ROM on my phone?
Yes. The patcher works in mobile Safari and Chrome. The patched ROM lands in your Downloads folder. Very large disc images may exceed a phone’s available memory, so those are better done on a computer.
Do I need to unzip the patch first?
No. Select the zip file directly and the patcher extracts the patch inside. If an archive contains several patches, you get a list to choose from.
Will patching modify my original ROM?
No. The original file on your disk is never written to. The patched ROM is built in memory and saved as a new download.
Which patch formats are supported?
IPS, BPS, UPS, APS (both N64 and GBA variants), RUP, PPF, BSDiff, xdelta/VCDIFF, EBP and Star Rod .mod files.
How do I know if the file I downloaded is a patch or a ROM?
Check the size and extension. A patch is usually kilobytes where a ROM is megabytes, and carries an extension like .ips, .bps, .ups or .xdelta. If you drop a file into the patch field and it is rejected, you probably picked the ROM by mistake.
My emulator says the patched file is invalid. What went wrong?
Most often the file is still a zip. Emulators such as Delta expect the ROM itself, so extract it first. It can also mean the patch was applied to the wrong base ROM, which produces a file that is the right size but not a working game.
Do I need RetroArch to play a patched ROM?
No. A patched ROM is an ordinary ROM file and runs in any emulator that supports the system. RetroArch is popular because it covers many consoles at once, but standalone emulators work identically.
Can I use a patched ROM on an Everdrive or a classic mini console?
On flash carts like the Everdrive, yes, since they load ROM files directly. Classic mini consoles need the ROM injected with their own tooling, which is a separate step from patching.
Which ROM should I download for a patch from a romhacking site?
The exact region and revision the readme names, for example "USA 1.0" rather than any USA copy. Where the author lists a CRC32 or MD5, verify against it with the checksum tool before patching. Guessing is what causes most failed patches.