Adding Mods

This guide covers how to prepare mod packages, organize them in the repository, and register them in Solder.

Repository Structure

Solder serves mod files from a repository directory defined by the SOLDER_REPO_LOCATION setting (see Configuration). Inside that directory, each mod gets its own folder named after its slug:

[repo_location]/
  mods/
    damage-indicators/
      damage-indicators-1.2.3.zip
      damage-indicators-1.2.4.zip
    buildcraft/
      buildcraft-7.1.23.zip
    forge/
      forge-1971.zip

Note

Slugs are always lowercase and use hyphens instead of spaces. The slug you choose here must match the Mod Slug you set in the Solder GUI.

Zip File Format

Each mod version is packaged as a zip file following this naming convention:

[mod-slug]-[version].zip

For example, a mod with slug damage-indicators at version 1.2.4 becomes damage-indicators-1.2.4.zip.

When the Technic Launcher installs a mod, it extracts the zip contents into the root of the modpack directory. This means the internal folder structure of the zip must mirror the directory layout expected inside a Minecraft instance.

Package Types

Different types of content require different internal zip structures.

Regular ModConfig PackForge LoaderFabric Loader

A standard mod jar goes inside a mods/ directory:

damage-indicators-1.2.4.zip
  mods/
    DamageIndicators-1.2.4.jar

Configuration files go inside a config/ directory. You can include files at other paths too -- everything extracts to the modpack root:

configpack-1.0.zip
  config/
    configA.cfg
    configB.cfg
  config.txt
  server.dat

Forge is packaged with the universal or installer jar renamed to modpack.jar inside a bin/ directory:

forge-1971.zip
  bin/
    modpack.jar

Use the Forge universal jar for Minecraft up to 1.12.2, and the Forge installer jar for Minecraft 1.13+.

Fabric uses a version.json file inside a bin/ directory. Follow the FabricMC wiki to generate this file:

fabric-loader-1.0.zip
  bin/
    version.json

Warning

Every mod package must contain the correct internal directory structure. If the zip is missing the expected folders (e.g. mods/ for a regular mod), the Technic Launcher will not install it correctly.

Adding a Mod via the GUI

1. In Solder, navigate to Mod Library > Add Mod.
2. Enter the Mod Name (e.g. Damage Indicators).
3. Verify the Mod Slug matches the folder name in your repository (e.g. damage-indicators).
4. Click Add Mod.
5. On the mod's page, go to the Versions tab.
6. Enter the version string in the Version field (e.g. 1.2.4). This must match the version portion of the zip filename.
7. Click Add Version, then click Verify to generate the MD5 checksum.

Tip

The Verify button connects to your mod repository and computes an MD5 hash of the zip file. If verification fails, double-check that the zip file exists at the expected path and that SOLDER_REPO_LOCATION and SOLDER_MIRROR_URL are configured correctly.

Using the Write API

Mods and mod versions can also be managed programmatically through the write API. This is useful for CI/CD pipelines or scripts that automate mod updates. See the Mods API reference for details.