Apply a ROM patch in the browser

Use the Apply page to combine your clean ROM with one or more patches. The original stays untouched and the new file never leaves your device.

Never done this before? Your first patch in the browser walks the same workflow with homebrew practice files first.

What do you need?

You need the patch and your own copy of the exact game release it was made for. Keep the patch author's notes open. Look for:

• region, such as USA, Japan, or Europe;
• revision, such as Rev 0 or Rev 1;
• a checksum and its algorithm;
• whether the ROM has a header;
• the required order when there is more than one patch.

Compare the checksum, not just the filename. How patching works explains the difference.

If you have a checksum but not the file, paste it into Identify by checksum. It sits under the drop zone on the empty page, and in 0x02 ROM once a patch is loaded. rom-weaver looks the checksum up in its local identification data and shows the expected ROM: its title, its region and revision, and every checksum and the size the data holds. Nothing is uploaded.

The search appears only while nothing else names the ROM. A bundle entry, or a patch that records its own source, already answers the question.

Keep one clean original somewhere safe. rom-weaver writes a separate result, but a known-good copy makes updates and troubleshooting much easier.

Add the files

1. Open Apply.
2. Drag the ROM and patch onto 0x01 Inputs, or choose Add files. You may add both at once.
3. Wait while the temporary cards say Reading or Checksumming.
4. If an archive contains several possible files, choose the entry the patch author named.

You can add supported archives, including ZIP, 7z, RAR, and tar, without extracting them first. rom-weaver looks inside, including inside nested archives. Disc containers such as CHD and RVZ are unpacked to the form the patch expects.

The page changes after the files are understood. 0x02 ROM holds the game, 0x03 Patches holds the patch stack, and 0x04 Apply controls the new file.

Read the ROM and patch cards

Start with the labels and warning colors, then open Checks if you need the numbers.

The ROM card shows the selected filename, size, detected system, and checksums. A message about the expected filename is advice. The name can differ while the bytes are still correct. A checksum or expected-size failure is strict and means the bytes do not match.

Each patch card shows its format and position. Open Checks to see what that patch expects at this point in the chain. Open the three-dot Patch actions menu to edit details, replace the file, or remove it. Header controls appear only for formats and systems where they make sense.

Put several patches in order

Patches run from top to bottom. Patch 2 receives the output of patch 1, not the clean ROM. Order is part of the release instructions.

Drag a numbered handle to move a patch. With a keyboard, focus the handle and use its announced controls. The number changes when the card moves.

The On or Off switch temporarily skips a patch. This is useful for optional add-ons, but only use combinations the author says are compatible. Turning off a required base patch can make everything below it fail.

After changing order or switches, read the checks again. A valid chain should show each patch matching the bytes produced by the step before it.

Choose the output and apply

If APPLY & DOWNLOAD is disabled, wait for reading and checksumming to finish. Read the nearby notice and resolve any failed checks.

In 0x04 Apply:

1. Enter an output filename without an extension.
2. Pick a plain file or a compressed output format. The format selector adds the extension.
3. Open Options only if you need compression, output header, or bundle controls. The defaults are right for most patches.
4. Choose APPLY & DOWNLOAD.
5. Wait for the button to finish, then save the browser download.

Everything happens locally in the browser. The ROM, patches, and result are not sent to rom-weaver - see why your files stay on your device.

Open a bundle

A bundle is a saved patching recipe. Add the bundle archive to 0x01 Inputs. If it is patch-only, rom-weaver shows which ROM it expects. Add your matching ROM. Review optional patch switches, then use APPLY & DOWNLOAD just as you would for loose files.

A release author can also give you a link that opens the bundle directly in Apply. The same local checks still happen before anything is written.

Want to publish one? Create and share a patch bundle has a separate browser-only guide and its own guided sample.

If the ROM does not match

Follow Fix a checksum error before applying. That guide checks region, revision, archive selection, headers, Nintendo 64 byte order, patch order, and earlier modifications. A different filename alone is advisory; a checksum or size mismatch blocks the run.

Use the result safely

Open the downloaded result in the emulator or hardware you trust. Reaching the title screen is a useful first check, but play far enough to exercise the change when you can. Some bad combinations fail later.

Do not delete the clean original. Give the patched result a name that includes the project and version so you can tell it apart later.

If you need automation or terminal commands, switch to the CLI apply guide. If you want to make your own change, continue with Create a ROM patch.