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CurseForge is one of the largest mod and modpack hosting platforms for Minecraft. Prism Launcher provides full integration for browsing, installing, and managing CurseForge modpacks.

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Overview

The CurseForge integration (internally called “Flame” after the API name) offers:
  • Extensive modpack library - Access to thousands of CurseForge modpacks
  • Advanced search and filtering - Find modpacks by category, mod loader, and version
  • Automatic dependency resolution - Downloads required mods automatically
  • Fingerprint matching - Accurate mod identification using file fingerprints
  • Update checking - Detect available updates for installed mods
  • Export functionality - Export instances as CurseForge modpacks

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Creating a CurseForge Instance

1

Open the New Instance dialog

Click Add Instance from the main window.
2

Navigate to CurseForge

Select the CurseForge tab in the new instance dialog.
3

Browse or search

Use the search bar to find specific modpacks, or browse by category and sorting options.
4

Select a modpack

Click on a modpack to view its description, author, and available versions.
5

Choose a version

Select your preferred version from the dropdown menu. The latest version is selected by default.
6

Create the instance

Click OK to begin downloading and installing the modpack.

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Sorting and Filtering

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Sort Options

CurseForge provides multiple sorting methods:
  • Featured - Highlighted and promoted modpacks
  • Popularity - Most popular modpacks
  • Last Updated - Recently updated modpacks
  • Name - Alphabetical order
  • Author - Sort by creator
  • Total Downloads - Most downloaded modpacks
  • Category - Group by category
  • Game Version - Sort by Minecraft version

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Filter Criteria

Filter modpacks by:
  • Mod Loader - Forge, NeoForge, Fabric, or Quilt
  • Minecraft Version - Specific game versions
  • Categories - Technology, magic, adventure, quests, etc.
CurseForge filtering uses category IDs internally. The launcher automatically translates user-friendly names to the correct category identifiers.

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Technical Implementation

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Flame API

The integration uses CurseForge’s Flame API, which provides: Project Search - /mods/search?gameId=432
  • Query modpacks with pagination
  • Filter by mod loader, version, and categories
  • Return project metadata and files
File Metadata - /mods/{modId}/files/{fileId}
  • Get specific file information
  • Download URLs and checksums
  • Changelog data
Fingerprint Matching - /fingerprints
  • Match installed files to CurseForge projects
  • Bulk fingerprint lookup for updates
  • Accurate mod identification

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Resource Type Class IDs

CurseForge uses class IDs to categorize content:
  • Mods: 6
  • Modpacks: 4471
  • Resource Packs: 12
  • Shader Packs: 6552
  • Data Packs: 6945
These class IDs are used in API requests to filter results to the correct content type.

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Mod Loader Types

The API uses numeric IDs for mod loaders:
  • Forge: 1
  • Cauldron: 2
  • LiteLoader: 3
  • Fabric: 4
  • Quilt: 5
  • NeoForge: 6

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Fingerprint Matching

CurseForge uses fingerprint-based file identification for accurate mod tracking.
1

Calculate file fingerprint

Prism Launcher computes a fingerprint hash for each installed mod file.
2

Submit to API

Fingerprints are sent to the /fingerprints endpoint in batches.
3

Match results

The API returns matching project and file IDs from CurseForge’s database.
4

Identify updates

Matched files are compared against the latest available versions.
Fingerprint matching only works for files originally downloaded from CurseForge. Manually added or modified files may not be recognized.

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Updating CurseForge Mods

Prism Launcher can check for and install updates to CurseForge mods.

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Update Detection

The launcher uses two methods:
  1. Fingerprint matching - Identifies current versions by file fingerprint
  2. Version comparison - Checks for newer file releases on CurseForge

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Smart Loader Selection

When multiple mod loaders are available, the launcher prioritizes:
  1. Mods matching your instance’s current loader (e.g., Forge)
  2. Mods compatible with your Minecraft version
  3. The most recently updated version if multiple matches exist
If a mod has versions for both Forge and Fabric, the launcher will select the version matching your instance’s mod loader, even if the other loader’s version is newer.

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Exporting to CurseForge

You can export your custom instances as CurseForge-compatible modpacks.
1

Select your instance

Right-click the instance you want to export.
2

Choose export format

Select Export Instance → CurseForge format.
3

Configure the export

  • Set pack name, version, and author
  • Choose which files to include (mods, configs, etc.)
  • Exclude client-only or server-only files if needed
4

Generate the pack

Save the .zip file containing the manifest and files.
The exported pack uses CurseForge’s manifest format: 
{
  "manifestType": "minecraftModpack",
  "manifestVersion": 1,
  "name": "My Modpack",
  "version": "1.0.0",
  "author": "YourName",
  "minecraft": {
    "version": "1.20.1",
    "modLoaders": [
      {
        "id": "forge-47.2.0",
        "primary": true
      }
    ]
  },
  "files": [
    {
      "projectID": 123456,
      "fileID": 789012,
      "required": true
    }
  ]
}

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Changelogs and Descriptions

The launcher can fetch additional information from CurseForge:
  • Mod descriptions - Full HTML descriptions from project pages
  • File changelogs - Release notes for specific versions
These are fetched on-demand when you view a mod’s details, reducing initial load time.

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Troubleshooting

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Common Issues

“Failed to download modpack”
  • Check your internet connection
  • Verify the modpack file is still available on CurseForge
  • Some files may require manual download due to redistribution restrictions
“Failed to resolve dependencies”
  • Some mods may have dependencies not hosted on CurseForge
  • Check the modpack description for manual installation steps
  • Update Prism Launcher to the latest version
“Update check failed”
  • Verify your CurseForge API key is valid (if required)
  • Check that mods were originally installed from CurseForge
  • Some mods may have been removed or hidden by authors
Due to CurseForge’s distribution terms, some mod authors restrict third-party downloads. In these cases, you may need to download files manually from the CurseForge website.

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API Requirements

Prism Launcher uses CurseForge’s public API. Starting in 2022, CurseForge requires API keys for some operations. Prism Launcher includes built-in API access, but high-volume users may need to provide their own API key.

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Source Code Reference

The CurseForge (Flame) integration is implemented in:
  • /launcher/modplatform/flame/FlameAPI.h - API client interface
  • /launcher/modplatform/flame/FlameAPI.cpp - API implementation
  • /launcher/modplatform/flame/PackManifest.h - Manifest parsing
  • /launcher/modplatform/flame/FileResolvingTask.cpp - Dependency resolution
  • /launcher/ui/pages/modplatform/flame/FlamePage.cpp - User interface