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.

01Practice with the included sample

Open guided Apply before using a game you care about. It loads a tiny homebrew NES ROM and two legal practice patches. The guide points at the same controls you will use with real files.

Patch 1 changes HELLO to MODIFIED. Patch 2 changes WORLD to ROM. Applying both in order gives MODIFIED ROM. The finished ROM's SHA-256 is e0db7cbd02cccd5e83931e7974db94aaafe40327b2a33fdd4c83235c9880a90e. That fingerprint lets you confirm your result is exactly the practice result.

You can choose Download a test bundle from the New here? beacon on the empty Apply page or download first-weave.zip. The archive contains the sample ROM, both IPS patches, and the recipe that puts them in order.

02What 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.

A filename is only a hint. Two different releases can have similar names. A checksum is calculated from every byte, so it is the useful proof.

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

03Add the files

1. Open Apply.
2. Drag the ROM and patch onto 0x01 Add files, or tap the large picker and select them. 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 ZIP, 7z, RAR, tar, and other supported archives 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 Weave controls the new file.

04Read 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.

05Put 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.

06Choose the output and weave

In 0x04 Weave:

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 WEAVE & 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. The privacy guide explains local browser storage and the small amount of normal site traffic.

07Open a bundle

A rom-weaver bundle is a saved patching recipe. It can include patch files, their order, optional choices, expected checksums, and output settings. A public bundle normally does not include the original game.

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

A release author can also give you a link that opens the bundle directly in Weave. 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.

08If the ROM does not match

Stop and find the difference. Do not turn on an override just to make the red message disappear.

Check these in order:

1. region and revision;
2. the selected file inside an archive;
3. header state;
4. Nintendo 64 byte order;
5. patch order;
6. whether the ROM was already patched or trimmed.

The checksum error guide explains each cause using the browser cards. A wrong filename by itself can be harmless. A wrong checksum or size is not.

09Use 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 complete CLI usage guide. If you want to make your own change, continue with Create a ROM patch. Back to the browser guide index.