Canonical: https://rom-weaver.com/docs/cli-create

# Create patches from the CLI

Build a patch from an original ROM and a modified one, and test the result before publishing it. New to the CLI? Start with [your first apply](<https://rom-weaver.com/docs/cli-get-started.md>).

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## Table of contents

- [Create a patch](<#create-a-patch>)
- [Pipe the patch to another program](<#pipe-the-patch-to-another-program>)
- [Test what you built](<#test-what-you-built>)
- [Where next](<#where-next>)

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## Create a patch

Build a patch from an original ROM and a changed one:

```bash
rom-weaver patch create \
  --original original.gba \
  --modified modified.gba \
  --format bps \
  --output release.bps
```

For a SOLID patch with game and author metadata:

```bash
rom-weaver patch create \
  --original original.sfc \
  --modified translated.sfc \
  --output translation.solid \
  --solid-system SNES \
  --solid-game "Example Game" \
  --solid-hack "English Translation" \
  --solid-version 1.0 \
  --solid-author "Example Team"
```

To create a patch from cheat codes instead of a changed ROM, see [Share a cheat as a patch](<https://rom-weaver.com/docs/bake-cheat-codes.md#share-a-cheat-as-a-patch>).

## Pipe the patch to another program

Set the patch format explicitly and use `--output -`:

```bash
rom-weaver patch create \
  --original original.gba \
  --modified modified.gba \
  --format bps --output - | gzip > release.bps.gz
```

The [binary pipeline reference](<https://rom-weaver.com/docs/cli.md#binary-pipelines>) lists storage requirements and incompatible options.

## Test what you built

Apply the created patch to the clean Original, then compare the rebuilt file with Modified:

```bash
rom-weaver patch apply -i original.gba --patch release.bps -o rebuilt.gba
rom-weaver checksum -i rebuilt.gba --algo sha256
rom-weaver checksum -i modified.gba --algo sha256
```

The SHA-256 values must match. Test the rebuilt file in the emulator or hardware you support. `patch validate` checks the values stored in the patch. It cannot compare with a separate Modified file, so keep the reconstruction check above.

## Where next

- Unsure which format to publish in? [Pick a patch format](<https://rom-weaver.com/docs/patch-formats.md>).
- Ship several patches with checksums and ordering as one file: [Weaves from the CLI](<https://rom-weaver.com/docs/cli-bundles.md>).
- Run `rom-weaver patch create --help` for every flag; the [CLI reference](<https://rom-weaver.com/docs/cli.md>) covers shared behavior.