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Feed The Beast (FTB) is one of the most established modpack platforms in the Minecraft community. Prism Launcher provides full support for browsing, installing, and managing FTB modpacks.

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Overview

The FTB integration offers:
  • Complete FTB catalog - Access to all public FTB modpacks
  • Version management - Install specific modpack versions
  • Featured packs - Highlighted and curated modpack collections
  • Automatic updates - Check for and install modpack updates
  • CurseForge integration - Many FTB packs use CurseForge mods
  • Legacy pack support - Import older FTB launcher modpacks

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Creating an FTB Instance

1

Open the New Instance dialog

Click Add Instance from the main window.
2

Navigate to FTB

Select the FTB tab in the new instance dialog.
3

Browse modpacks

Browse the FTB catalog or use the search bar to find specific packs.
4

Select a modpack

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

Choose version

Select your preferred version from the dropdown menu. Available versions are listed with their Minecraft version.
6

Create the instance

Click OK to download and install the modpack.

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Modpack Information

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Pack Metadata

FTB modpacks include rich metadata:
  • Name and synopsis - Pack title and short description
  • Description - Full pack overview and features
  • Authors - Pack creators with links to their profiles
  • Tags - Categories like “Magic”, “Tech”, “Expert”, etc.
  • Art assets - Pack logo and banner images
  • Featured status - Whether the pack is featured on FTB
  • Install/play counts - Popularity metrics

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Version Information

Each version provides:
  • Version name - Release identifier (e.g., “1.0.0”)
  • Minecraft version - Compatible game version
  • Version type - Release, beta, or alpha
  • System requirements - Minimum and recommended RAM
  • Mod loader targets - Required Forge/Fabric versions
  • File list - All included mods and files
  • Update timestamp - When the version was released
FTB modpacks often have specific memory requirements. Pay attention to the recommended RAM listed in the version details.

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Sorting and Filtering

The FTB browser provides several sorting options:
  • Featured - FTB’s highlighted modpacks
  • Popularity - Most played modpacks
  • Installs - Most installed packs
  • Name - Alphabetical order
  • Updated - Recently updated packs
  • Released - Newest releases
Use the search bar to filter by:
  • Pack name
  • Author
  • Tag or category

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Technical Implementation

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FTB API Structure

The integration uses FTB’s modpack API, which provides: Modpack Listings 
{
  "id": 123,
  "name": "FTB Infinity Evolved",
  "synopsis": "A kitchen sink modpack",
  "type": "modpack",
  "featured": true,
  "installs": 1000000,
  "plays": 5000000,
  "tags": [
    {"id": 1, "name": "Magic"},
    {"id": 2, "name": "Tech"}
  ],
  "versions": [
    {
      "id": 456,
      "name": "3.0.0",
      "type": "release"
    }
  ]
}
Version Details 
{
  "id": 456,
  "name": "3.0.0",
  "specs": {
    "id": 1,
    "minimum": 4096,
    "recommended": 6144
  },
  "targets": [
    {
      "id": 1,
      "type": "game",
      "name": "minecraft",
      "version": "1.20.1"
    },
    {
      "id": 2,
      "type": "modloader",
      "name": "forge",
      "version": "47.2.0"
    }
  ],
  "files": [
    {
      "id": 789,
      "type": "mod",
      "name": "example-mod.jar",
      "path": "mods/example-mod.jar",
      "url": "https://...",
      "sha1": "abc123",
      "size": 1024000,
      "clientOnly": false,
      "serverOnly": false,
      "optional": false
    }
  ]
}

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File Types

FTB packs can include various file types:
  • Mods - Standard mod files
  • Config - Configuration files
  • Scripts - CraftTweaker/KubeJS scripts
  • Resources - Resource pack files
  • Overrides - Custom files that override defaults

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CurseForge Integration

Many FTB modpacks source mods from CurseForge. Files include CurseForge metadata: 
{
  "curseforge": {
    "project_id": 123456,
    "file_id": 789012
  }
}
This allows Prism Launcher to:
  • Download mods from CurseForge CDN
  • Check for mod updates
  • Resolve dependencies
FTB packs that use CurseForge mods benefit from CurseForge’s CDN for faster downloads and better availability.

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System Requirements

FTB modpacks specify memory requirements in megabytes:
  • Minimum - Bare minimum to run (may have performance issues)
  • Recommended - Suggested allocation for smooth gameplay

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Setting Memory Allocation

1

Edit instance settings

Right-click the instance and select Edit Instance.
2

Navigate to Settings

Click on the Settings page.
3

Enable custom memory

Check Override global memory settings.
4

Set allocation

Adjust the Maximum memory allocation to the recommended value or higher.
Allocating too little memory will cause crashes. Allocating too much can reduce performance due to garbage collection overhead.

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Optional and Client/Server Files

FTB modpacks can specify file installation rules:
  • clientOnly - Only installed on clients, not servers
  • serverOnly - Only installed on servers, not clients
  • optional - User can choose to install or skip
Prism Launcher automatically handles these flags during installation.

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Art Assets

FTB modpacks include art assets with metadata:
  • URL - Location of the image
  • Type - Logo, banner, or background
  • Dimensions - Width and height
  • SHA-1 hash - For verification
  • Size - File size in bytes
  • Compressed - Whether the image is compressed
The launcher downloads and caches pack art to display in the modpack browser.

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Legacy FTB Packs

Prism Launcher also supports importing modpacks from the legacy FTB launcher.
1

Locate FTB legacy instance

Find your FTB launcher installation directory.
2

Import instance

Use File → Import Instance and select the legacy FTB folder.
3

Convert

Prism Launcher will convert the instance to its native format.
Legacy FTB packs are stored in a different format but can be imported and managed like any other instance.

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Updating FTB Modpacks

When a new version of an FTB modpack is released:
1

Check for updates

The launcher can detect when newer versions are available.
2

Review changes

Check the modpack’s changelog to see what’s new.
3

Update instance

Create a new instance with the updated version, or manually update mods.
4

Migrate saves (optional)

Copy your world saves to the new instance if needed.
Updating to a major new version may not be save-compatible. Always back up your worlds before updating.

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Troubleshooting

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Common Issues

“Failed to load FTB modpack list”
  • Check your internet connection
  • Verify FTB’s API is accessible
  • Try refreshing the modpack browser
“Out of memory” errors
  • Increase maximum memory allocation
  • Close other applications to free RAM
  • Check that your system meets the pack’s requirements
“Failed to download files”
  • Some mods may temporarily be unavailable
  • Check if CurseForge integration is working
  • Verify you have enough disk space
“Pack won’t launch”
  • Verify Java version compatibility
  • Check mod loader installation
  • Review console output for error messages

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CurseForge Dependencies

Since many FTB packs use CurseForge mods, ensure your CurseForge integration is working properly. See the CurseForge documentation for more details.

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Source Code Reference

The FTB integration is implemented in:
  • /launcher/modplatform/ftb/FTBPackManifest.h - Pack manifest structures
  • /launcher/modplatform/ftb/FTBPackInstallTask.cpp - Installation logic
  • /launcher/modplatform/legacy_ftb/ - Legacy FTB launcher support
  • /launcher/modplatform/import_ftb/ - FTB pack import functionality
  • /launcher/ui/pages/modplatform/ftb/FtbPage.cpp - User interface

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