How to Create an XDelta Patch on Android with UniPatcher

An XDelta patch records the differences between an original file and a modified copy. It lets you share those changes without packaging the complete game file. Put the original and modified versions in the correct fields, since reversing them would describe the opposite transformation.

Original sourceBefore changesModified fileAfter changesXDelta patchThe differences

Preparation

Understand the three file fields

The labels describe different stages of the same file, not interchangeable inputs.

Source file: The original or base file before your modifications were made.
Modified file: The changed copy containing everything you want the patch to represent.
Patch file: The new .xdelta output that UniPatcher will generate.

Step 1

Open the Create patch screen

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Check the current screen

UniPatcher normally opens on Apply patch. Check the heading at the top before opening the navigation drawer.

UniPatcher screen with a red arrow pointing to the Apply patch heading — First confirm that the heading says Apply patch.

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Tap the three-line menu icon in the upper-left corner. This opens UniPatcher's navigation drawer.

UniPatcher Apply patch screen with the upper-left menu icon marked by a red arrow — Tap the menu icon in the upper-left corner.

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Choose Create patch

In the navigation drawer, tap Create patch. Do not choose Apply patch, which is the screen you are leaving.

UniPatcher navigation drawer with Create patch marked by a red arrow — Select Create patch in the navigation drawer.

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Confirm the Create patch screen

Check that the heading now reads Create patch. The screen should contain Source file, Modified file and Patch file.

UniPatcher Create patch screen with its heading marked — The Create patch heading confirms that you are in the correct section.

Step 2

Select the original source file

Source file means the unchanged original before your modifications were made. Use the exact file from which your modified version was created.

The screenshots use Trashman Emerald.gba only as an example; your source filename will depend on your own project.

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Tap the Source file selector

Tap tap to select beneath Source file. Android's file picker will open.

UniPatcher Create patch screen with the Source file selector marked — Tap the selector beneath Source file.

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Choose and confirm the original file

Select the unchanged original. When UniPatcher returns, confirm that its filename appears beneath Source file.

UniPatcher Create patch screen showing Trashman Emerald dot gba selected as the source — The original filename now appears under Source file.

Step 3

Select the modified file

Modified file is the changed version containing everything you want the XDelta patch to represent.

The example displays an Emerald Imperium file only to demonstrate the interface. UniPatcher compares the files you provide; it does not supply them or determine whether the modified version contains the changes you intended.

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Tap the Modified file selector

Tap tap to select beneath Modified file to open Android's file picker.

UniPatcher Create patch screen with the Modified file selector marked — Use the second field for the version containing your changes.

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Choose and confirm the modified file

Select the changed copy. When you return to UniPatcher, verify that its filename appears beneath Modified file and that the original remains in Source file.

UniPatcher Create patch screen with source and modified filenames selected — Both input filenames should now appear in their correct fields.

Step 4

Choose where to save the XDelta patch

Patch file is the new .xdelta output that UniPatcher will generate. It records the differences between the source and modified files.

Choose a name that identifies the project and version without implying that the patch contains the complete game. The screenshots use emerald Imperium.xdelta as an example destination.

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Open the Patch file selector

Tap tap to select where to save the patch beneath Patch file.

UniPatcher Create patch screen with the Patch file destination selector marked — Open the Patch file selector after choosing both inputs.

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Name and save the XDelta file

In Android's save interface, choose a folder, enter a useful filename ending in .xdelta, and tap Save.

Android save dialog showing an XDelta filename and the Save button marked — Name the output, retain .xdelta and tap Save.

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Confirm the patch destination

When UniPatcher returns, check that the new .xdelta filename appears beneath Patch file.

UniPatcher Create patch screen showing the XDelta output filename selected — Confirm that the .xdelta destination appears in the Patch file field.

Step 5

Create the XDelta patch

Review the three fields one last time: unchanged original in Source file, changed copy in Modified file, and a new .xdelta destination in Patch file.

Tap the red action button

Tap the red round action button in the bottom-right. Keep UniPatcher open while it compares the files and writes the patch; larger files or slower storage may take longer.

Step 6

Confirm that the patch was created

Wait for the confirmation message

Keep the app open until Patch created appears. This message confirms that UniPatcher wrote the new XDelta file to your selected location.

UniPatcher notification reading Patch created after generating the XDelta file — Patch created confirms that the .xdelta output was written.

The .xdelta file can now be distributed separately from the game and applied to the correct compatible source file.

Before sharing it, test the patch against a clean copy of the same source file. A successful test checks that someone starting with the documented original can reproduce your modified result.

How to Create an XDelta Patch on Android Using UniPatcher