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What is it

ATLauncher is a launcher for Minecraft which integrates multiple different modpacks to allow you to download and install modpacks easily and quickly.


Contributing to ATLauncher

Take a look at


Please see the file for information on how we write tests.


In order to build ATLauncher, you will need any Java version 8 or above. Java 8 is recommended since we compile to Java 8 compatability regardless.

Everything else that's needed for the project is provided by Gradle, and accessed using the Gradle wrapper which can be invoked by using ./gradlew.


To build this project, simply run:

./gradlew build

This will build the application and output the resulting files for Windows, Linux and OSX in the dist directory.

Running in test

If you want to run the launcher while developing with it, you can use your IDE (if you have one) to do that for you.

Alternatively you can run:

./gradlew run --args="--debug --working-dir=testLauncher"

Setting the --working-dir=testLauncher argument is necessary as it will ensure that the launchers files are not spewed in the root directory and are instead contained within a gitignored folder.

Using an IDE

This project is mainly setup and developed to use VSCode for development. You're free to use any other IDE that you're accustomed to (if any), but by using VSCode, you get the benefit of predefined tasks and launch commands as well as a list of extensions recommended for the project.

We also provide some base project files for IntelliJ IDEA so that if you use that, you should get access to our base project files which contain correct launch tasks for testing the application as well as tasks for running the UI/Unit tests.

Checking for dependency updates

To check for dependency updates with gradle, simply run:

./gradlew dependencyUpdates

This will print a report to the console about any dependencies which have updates.

Updating license headers in all files

If you add new files, or update the LICENSEHEADER file, you can add that to all source files by running:

./gradlew updateLicenses

To check that they're all correct, you can run the below command:

./gradlew checkLicenses

This is run during the CI process, and will fail if the license is missing or not up to date, so make sure that you add this to all new files you create.

Create Custom Themes

ATLauncher supports custom themes. The process is fairly straight forward, but may require a lot of trial and error.

First you must create a in the src/main/java/com/atlauncher/themes/ directory. Your theme should extend one of the base ATLauncher themes depending on what you need:

  • Dark is the default theme and is a dark theme. It's a good place to start with some defaults for new dark themes.
  • Light is a light theme. It's a good place to start with some defaults for new light themes.
  • ATLauncherLaf is a base class which every theme MUST at some point extend. It provides some defaults including our brand colours and some defaults. This shouldn't be extended from unless you need absolute power.

Once you've created your class (look at other themes in the directory for an idea on what you can do), you'll need to create a properties file in the src/main/resources/com/atlauncher/themes/ directory. This properties file is how you setup and change UI elements. You should use the existing examples in that directory as examples.

Last step is to register the theme in the file src/main/java/com/atlauncher/gui/tabs/settings/

Now you can open the launcher and then switch to your theme.

We use a library called FlatLaf to provide theme support. There are some good references listed below to see the default values for the themes and see what you can overwrite:

IntelliJ theme.json Support

You can also take IntelliJ theme.json files and convert them to themes for ATLauncher. From within the theme.json file, take the UI object and plug that into this site to convert it from JSON to properties format.

There are also special rules you need to apply as we currently do not support these theme.json files out of the box, so you need to manually apply the transformations in order for the theme to work exactly right.

For an example, see the DraculaContrast theme which uses this method.

Tools To Help Theme Development

To help with theme development, with the launcher running (not in the release version, only in development), you can press Ctrl + Shift + Alt + X to bring up a tool to highlight UI components to see their properties. You can also press Ctrl + Shift + Alt + Y to bring up a list of all the default properties in the UIManager. These values can be modified in your .properties file.

Plugging In Your Data

To get started with the code and plug in your own data, you need to edit the /src/main/java/com/atlauncher/constants/ file.

By using this source code you don't get permissions to use our CDN/files/assets/modpacks. See the License section at the bottom for more.

Most of of them should be self explanatory, if not please stop by our Discord and ask in the #development channel if you need help understanding any of the values.

A couple values in the constants file are specific for ATLauncher and shouldn't be used in any forks. These are the CurseForge Core api key and the Microsoft Login Client ID.

You can apply for a CurseForge Core key through this link and a Microsoft Login Client ID through this link.

Versioning System

Starting with version a new versioning system was put into place. It works off the following:


So for the major number is 2 and minor number is 1 and revision number is 0. Reserved is used as a base, only incremented on complete rewrites. The stream is optional.

Major should be incremented when large changes/features are made.

Minor should be incremented when small changes/features are made.

Revision should be incremented when there are no new features and only contains bug fixes for the previous minor.

Build is used for beta releases allowing you to have higher version numbers but force users to update when the real release comes.

Stream is used to define if it's a "Release" or a "Beta". When not provided, it defaults to "Release".

Updating The Version

The version can be updated in a single place in the /src/main/resources/version file.

The stream value doesn't need to be provided, but should only ever be "Beta". When a release is ready to go out, the stream should be removed from the version so that everything will automatically release.


ATLauncher is written for English speakers. All our translations are community run by those who take their time and submit updates to the text in a different language.

If you wish to help translate ATLauncher, please visit our page on Crowdin and start translating.

Updating the template file

Every push to master will automatically add any new strings that need translating via GitHub actions.

Manual Steps

If new strings are added to the launcher, the template file will need to be updated in order to take into account the new strings.

In order to do this, run ./gradlew generatePots which will scan the source files and create a build/gettext/translations.pot file.

Note that out of the box, this will not generate in the correct format. You must run the deduplicateTranslations script in the scripts/deduplicateTranslations folder which will use Docker to fix the translations.pot file.

This file can then be uploaded to Crowdin by ATLauncher staff to give access to the translators.

Adding new languages from Crowdin

Running this action will download all approved translations strings and make a commit to master with then changed language files.

Manual Steps

Once a language has been translated enough to add support to the launcher (or update support) there's a few steps we need to take.

First grab the built project from Crowdin, and then grab out the translation to add/update. For this example, let's take German.

Pop this file in the scripts/processTranslations/in directory and then run the scripts/processTranslations.bat or scripts/ file to fix them up and output them into the scripts/processTranslations/out directory.

Now take the converted files from the scripts/processTranslations/out directory and put them in the src\main\resources\assets\lang directory.

Now open src\main\java\com\atlauncher\data\ and in the static block at the top, add in the language:

// add in the languages we have support for
static {
    locales.add(new Locale("de", "DE"));

Now the launcher should have the option to change to the language/s.


This work is licensed under the GNU General Public License v3.0. To view a copy of this license, visit

A simple way to keep in terms of the license is by forking this repository and leaving it open source under the same license. We love free software, seeing people use our code and then not share the code, breaking the license, is saddening. So please take a look at the license and respect what we're doing.

Also, while we cannot enforce this under the license, you cannot use our CDN/files/assets/modpacks on your own launcher. Again we cannot enforce this under the license, but needless to say, we'd be very unhappy if you did that and really would like to leave cease and desist letters as a last resort.

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