Delta Patcher Features

The core feature. Choose an Original file and an XDelta patch, click Apply patch, and Delta Patcher rebuilds the modified file using xdelta3. It opens in this mode every time it starts.

Practical example

You download a fan translation distributed as a .xdelta file, select your own copy of the game image, and apply it in a few clicks.

Who benefits

Anyone who’s been given a patch and wants to use it without learning command-line tools.

Step-by-step: how to apply a patch →

Switch to patch creation mode to compare an Original file with a Modified file and save the differences as a new .xdelta patch. The patch is a standard xdelta3 file that other XDelta tools can apply too.

Practical example

A modder finishes editing a disc image and creates a small patch to share instead of the full image.

Who benefits

Translators, modders and developers distributing changes to files.

How to create an XDelta patch →

When applying, Checksum validation (on by default) checks every rebuilt window against the Adler-32 checksums stored in the patch and stops on a mismatch. When creating, Add Checksum to patch (also on by default) writes those checksums, so your users get the same protection.

Since version 3.1.2, the most common failure shows a plain-language message: “The file you are trying to patch is not the right one.”

Practical example

Someone tries a European patch on a US game image. Instead of producing a corrupted file, Delta Patcher stops and explains the file isn’t the right one.

Who benefits

Everyone. It turns a silent, confusing failure into a clear error.

What a checksum mismatch means →

Delta Patcher writes the patched file next to the original. With Backup original file off (the default), a successful patch replaces the original. With it on, the original stays and the result is saved as namePATCHED.ext. The setting isn’t remembered between launches.

Practical example

You want to compare the patched and unpatched versions, so you tick the option and get Game (USA).iso and Game (USA)PATCHED.iso side by side.

Who benefits

Anyone without a separate backup of their original file.

Where the patched file is saved →

Patches created with Delta Patcher can include a Unicode description. When someone loads that patch, Delta Patcher shows the text in a Patch info tooltip (since 3.1.2; earlier versions printed it in the log). The description lives in the patch’s VCDIFF application header, so other tools can still apply the patch.

Practical example

A patch author writes “Apply to Game (USA).iso, revision 1.0” plus its SHA-1, and users see it as soon as they select the patch.

Who benefits

Patch authors who want fewer support questions, and users who need to know which source file to use.

Writing a useful description →

In application mode, drop files anywhere on the window: a file ending in .xdelta goes into the XDelta patch field and anything else into the Original file field. In creation mode, drop files directly onto the Original file or Modified file fields.

Practical example

You drag a game image and then a patch from your file manager, and both fields fill in without a single file dialog.

Who benefits

Anyone who patches files often.

When creating patches, set the Main compression level from 0 to 9 (default 5) and choose Secondary compression: lzma, djw, fgk or none (default). Delta Patcher can apply patches that use any of these compressors.

Practical example

For a large translation patch, a creator uses level 9 with lzma to cut the download size, knowing their users run a current Delta Patcher.

Who benefits

Patch authors distributing large patches.

What each creation option does →

Src Window Size sets how much of the original file xdelta3 searches at once when creating a patch: Auto (xdelta3’s 64 MB default) or 8 MB to 1024 MB. Larger windows find matches for data that moved further, which can shrink patches for big files.

Practical example

A patch for a 4 GB image with a new file inserted near the start comes out much smaller after raising the window to 512 MB.

Who benefits

Authors of patches for large disc images.

How the source window works →

Delta Patcher can apply and create patches for files larger than 4 GB, such as dual-layer DVD images. Version 3.1.5 added this and updated the embedded xdelta3 library to 3.1.0.

Practical example

Applying a patch to a 7 GB disc image works without switching to the command line.

Who benefits

Anyone working with DVD-sized or larger images.

Many XDelta GUIs are front-ends that run a separate xdelta3 executable. Delta Patcher compiles xdelta3 3.1.0 into the program as a library, with its libraries statically linked (except GTK on Linux). There’s no xdelta3 install, no .NET runtime, and since 3.0.0 no helper executable extracted at runtime, a change the changelog says was made to avoid antivirus false positives.

Practical example

You copy the program to a new PC and it works immediately, with nothing else to install.

Who benefits

Anyone who wants a tool that just runs, including on locked-down or offline machines.

Delta Patcher uses wxWidgets, so it looks and behaves like a native app on each system. Current builds: Windows 7 or later in 64-bit and 32-bit, macOS 11 Big Sur or later as a universal app for Apple silicon and Intel, Linux x86-64 with GTK 3, and Flathub for x86-64 and ARM64 (Flatpak support added in 3.1.3).

Practical example

A translation team writes one set of instructions that works for users on all three systems.

Who benefits

Mixed-platform communities and anyone on macOS or Linux, where XDelta GUIs are rarer.

Installation guide for each system →

Delta Patcher accepts a .xdelta file as a start-up argument and loads it into the XDelta patch field. That means you can associate .xdelta files with Delta Patcher and double-click a patch to open it ready to apply.

Practical example

After setting Delta Patcher as the default app for .xdelta files, double-clicking a patch opens it with the patch already selected.

Who benefits

People who apply patches regularly.

Set up the file association on Windows →

A timestamped log records each file selected and every result, including the exact xdelta3 message when something fails. Since 3.1.2 the log is hidden by default to keep the window compact; the bottom-right button shows it.

Practical example

A patch fails with “See log for more information”; the log shows file open failed, pointing to a permissions problem.

Who benefits

Anyone troubleshooting, and helpers who need the exact error text.

How to read the log →

On Windows 10 and later, Delta Patcher follows the system dark mode setting. Version 3.1.3 added proper scaling for high-DPI displays, and 3.1.4 fixed button alignment on modern macOS.

Practical example

On a 4K laptop screen with dark mode on, the window renders sharply and matches the rest of the system.

Who benefits

Users on modern displays and systems.

Delta Patcher is released under the GNU General Public License v2.0. The full source code, build instructions and issue tracker are on GitHub (opens external site), and anyone can build it with CMake.

Practical example

A Linux distribution packager builds Delta Patcher from source, and a curious user reads exactly how output files are named.

Who benefits

Anyone who values transparency, and developers who want to learn from or contribute to it.