Publish mods for Modsy Desktop

Before you start

Desktop publishing supports Euro Truck Simulator 2 and American Truck Simulator. You need a Modsy modder account and a ZIP containing compatible SCS files. Your normal membership upload and storage allowances apply, including on the free plan.

Publish from Modder Dashboard → Mods on the website. Players use Modsy Desktop to install your releases. You do not need to create your own installer or register an app ID; the separate Desktop App Auth API guide is for modders building their own software.

Prepare compatible files

• Put your .scs files inside one .zip. Include the actual SCS files, rather than another ZIP or an installer that produces them.
• Supported SCS formats include ZIP-based SCS archives and supported native HashFS v2 / CITY archives. A .scs extension alone does not guarantee compatibility; Modsy checks the file contents.
• Use complete, undamaged archives without passwords or encryption. Custom protection or other archive formats may be incompatible; check the compatibility result before publishing.
• The SCS files must work in the selected game versions without running a bundled installer. Desktop installs SCS files only; executables and other unsupported companion files are excluded. The original ZIP remains available when web downloads are enabled.
• Test the files in-game. Passing the upload check confirms package compatibility, but does not confirm that your mod works correctly in the game.

Desktop adds account-linked fingerprints to installed SCS files for leak tracing. Original web ZIP downloads are not fingerprinted. If you want every download to go through Desktop, choose Modsy Desktop only downloads.

Publish a mod

1. Open Modder Dashboard → Mods → Upload New Mod.
2. Complete the mod details, choose the correct game and compatible game versions, and select your ZIP.
3. Wait for the Desktop compatibility check, then choose a Download options setting:
   • Web downloads: players download the original ZIP from the website.
   • Web + Modsy Desktop downloads: players can use either method, with one ZIP and one mod version.
   • Modsy Desktop only downloads: players install through Desktop; the original ZIP cannot be downloaded from the website.
4. Review the detected SCS files. Use Customize installation if you need optional add-ons, game settings, or activation instructions.
5. Confirm that you tested the files and settings with the selected game versions. Complete the file-assignment review checkbox if shown, then submit.
6. Keep the upload window open until Desktop preparation finishes. New mods still go through the normal review process.

Public, Premium, and Early Access rules still apply. Enabling Desktop does not grant players access to restricted content.

Add an existing web-only mod to Desktop

Release a new update with Desktop selected. You do not need to change the mod files.

Open your existing mod's New version action, enter a new version number, and upload the same ZIP if its SCS files are already compatible. Choose Web + Modsy Desktop downloads or Modsy Desktop only downloads, review the installation setup, and publish. A short changelog such as “Added Modsy Desktop installation support; mod files unchanged” helps players understand the update.

This adds Desktop support to the new version. Earlier web-only versions keep their existing download options. If the compatibility check fails, resolve the reported file issue before enabling Desktop.

Release new updates for Desktop users

1. In Modder Dashboard → Mods, select New version on the same mod.
2. Enter a new version number and changelog, select compatible game versions, and upload the updated ZIP.
3. Check Download options for this release and select a Desktop option.
4. Review the previous installation setup that Modsy carries forward. If an SCS file was renamed, moved, or removed, use Match files from the previous version to choose its replacement or remove it from this version. Renaming the outer ZIP does not require matching.
5. Review newly added SCS files: they start as optional add-ons when reusing a previous setup. Mark files required if every player needs them. Check game settings and installation notes too.
6. Test, confirm the checkboxes, select Publish Version, and wait for Desktop preparation to finish.

Once the version is available under its release and access rules, players can install the update through Modsy Desktop. Keep using the same mod listing so releases remain together in its version history.

Choose files and explain installation

Open Customize installation → Files and optional add-ons. A fresh setup makes all detected SCS files required. Required groups install automatically; optional add-ons start unselected and players choose them. Files in a group install together.

Use Make optional to separate an add-on, and give groups clear names. Assign every SCS file once, keep at least one required group, and use unique installed filenames. When matching update files, keep the existing groups where possible to preserve their settings and installation choices.

Under Installation instructions, explain activation and load order in up to 500 characters. For example: “Activate Main files in the game's Mod Manager. Place the compatibility patch above the main mod.” Installation copies files; players still need clear instructions about what to activate in-game, especially when alternatives must not be active together.

Request game configuration changes

Leave Game settings empty unless your mod requires a configuration change. To add one, open Customize installation → Game settings → Add required setting and complete:

• Applies with: the file group that needs this setting. A setting attached to an optional add-on applies when that add-on is selected.
• Config file: Game config for the game's main config.cfg, or Profile config for the local or Steam Cloud profiles the player selects.
• Attribute: the existing setting name only, such as g_truck_stability.
• Value: the required value without surrounding quotes, such as 0.5.
• Why this change is needed: a short explanation players can understand.

For example, if your tested physics mod requires uset g_truck_stability "0.5" in the profile config, choose Profile config, enter g_truck_stability as the attribute and 0.5 as the value, then explain why your mod needs it. Use your own tested value; this example is not a recommendation for every mod.

Players preview and approve the changes. Profile settings apply only to their selected profiles. Desktop changes existing attributes; it does not create missing settings or config files. Missing or ambiguous attributes, unavailable profiles, or conflicting requirements from installed mods can stop installation. Verify the correct config scope, attribute, and value for every game version you select.

Check and manage your release

Before announcing the release, test installation through the current Modsy Desktop app with an account that has access. Check required files, optional add-ons, any config prompts, and in-game activation. For an update, also test updating a previous installation.

If the upload says Mod saved or Version saved but Desktop preparation needs attention, use Retry Desktop preparation in the upload window. Saving the version alone does not mean Desktop downloads are ready. Desktop-only downloads remain unavailable until preparation succeeds.

Use Manage Versions → Desktop downloads to check a version's package status, disable future Desktop installations, or cancel unfinished preparation. Disabling a package leaves already installed files on players' computers. Cancelling preparation cannot be resumed from Manage Versions. Publish a new version when you need to change files or installation settings for a released package.