Asset File Format and Structure Requirements

Fab provides high-quality, ready-to-use game development content (such as 3D models, animations, and audio) for all developers, from students to AAA studios. This means that all assets offered on Fab must meet the criteria on this page.

This page contains a summary of the technical requirements for Fab assets. For full details, see the Fab Technical Requirements. Fab assets must also meet the content criteria in the Fab Terms of Service and Epic Content Guidelines.

In Fab:

• An asset is a standalone item, such as a 3D model, that you offer for sale or for free.
• A product is a general way to refer to items for sale. Can be an individual asset or a pack.
• A pack is a single product that contains many individual assets.
• A listing is a page in Fab a publisher uses to offer products for sale or for free.
• You publish a listing to make the listing visible, and the associated product available to buy or download.

General Technical Requirements

Your listings and assets must follow these requirements:

• Your assets must not contain visual defects.
• Your products must be complete.
• Your products must function as you describe them in your listings.
• If you include additional files, they must relate to the product listing they are included with.

Accepted Asset Formats

Fab accepts the following asset formats.

2D assets

2D assets for building 2D content.

Game engines

• Unreal Engine
• Unity

3D models

3D meshes can contain attributes such as "animation" or "rigged".

Game engines

• Unreal Engine
• Unity

3D exchange formats

• FBX
• GLB
• GLTF
• OBJ
• USD
• USDZ

3D DCC

• 3ds Max
• Blender
• Cinema 4D
• Maya

Animations

Motion-captured animations to animate characters and objects.

Game engines

• Unreal Engine
• Unity

Audio

Sounds and music.

Game engines

• Unreal Engine
• Unity

Education & Tutorials

Learning resources

Game engines

• Unreal Engine
• Unity

Environments

Asset packs used to create and customize environments and scenes

Game engines

• Unreal Engine
• Unity

Game Systems

Assets that use a game engine's functionality to provide ready-made features for game making or gameplay.

Game engines

• Unreal Engine
• Unity

Game Templates

Pre-built game templates or kits for speedy game development.

Game engines

• Unreal Engine
• Unity

HDRI

HDR images are typically used in 3D computer graphics to create realistic lighting and reflections.

Game engines

• Unreal Engine
• Unity

Material & Textures

Tileable assets that can be applied to a mesh to alter its visual appearance.

Game engines

• Unreal Engine
• Unity

Smart Assets

3D Meshes with scripts that allow user interaction.

Game engines

• Unreal Engine
• Unity

Tools & Plugins

External or third-party tools and plugins that add additional features and functionality to gameplay or the game-making process.

Game engines

• Unreal Engine
• Unity

User Interfaces (UI)

On-screen elements that provide information, and menus and screens that are used to navigate a software product.

Game engines

• Unreal Engine
• Unity

Visual Effects (VFX)

Particle systems that add gameplay or peripheral art effects to a project

Game engines

• Unreal Engine
• Unity

File Format Requirements

Assets

The following file size limits apply for assets:

• Unreal Engine file format: If possible, keep the file size to 15GB or less. If your file is larger than 15GB, the Fab team reviews the file to determine if the larger size is necessary.
• Unity file format: The size limit is the same as for the Unity Asset Store. See the Unity Asset Store documentation.
• For files with the type "Additional Files", the size limit is 6GB. You can have up to three of these files on a listing, for a maximum total of 18GB.
• For all other file types, the size limit is 6B. You can have up to one file of each file type on a listing.

Media Gallery Images

The requirements for each media gallery 2D image are as follows:

• Minimum Image size: 1920 x 1080 pixels
• File size: less than 3MB
• File format: JPEG or PNG

The 2D images in the media gallery must be less than 25MB in total.

3D previews in the media gallery must be less than 500MB.

Unreal Engine Project Format

If your product is an Unreal Engine project, then it must follow the technical guidelines in this section.

This section provides a summary of the technical requirements. For full details, see the Fab Technical Requirements. Fab assets must also meet the content criteria in the Fab Terms of Service and Epic Content Guidelines.

Content Product

A content product is any product that is not a code plugin.

Content product must not contain any C++ code.

You must upload your content product as an Unreal Engine project that contains the following:

• .uproject file
• Content directory
• Config directory

The Content directory must only contain one subdirectory. This subdirectory must be named after your product (the Pack directory) and it should contain all other directories and assets.

The directory structure must be as follows:

• MyProject
  • Config
  • Content
    • MyProject
  • MyProject.uproject

Unreal Engine Code Plugins

The following guidelines apply to Code Plugins:

• Code Plugins must contain at least one code module.
• Code Plugins can contain any content that you need in order for the plugin to function appropriately.

Make sure that your Code Plugins offer base functionality so that the product has inherent value for buyers. You can include additional functionality through a license or subscription model if your product meets the following requirements:

• The Fab minimum content standards.
• The Fab quality standards.
• Includes enough functionality to stand on its own.

All Code Plugin products must contain the following:

• .uplugin file
• Source directory
• Content directory
• Config directory

The directory structure must be as follows:

• MyPlugin
  • Config
  • Content
  • Resources
  • Source
  • MyModule
  • Private
  • Public
  • MyModule.build.cs
  • ThirdParty
• MyPlugin.uplugin

Other guidelines:

• You must compress the project into a .zip file before you upload it to Fab.
  • You can password protect your .zip file, but you must provide the password in the Version Notes section of the Fab listing.
• The download link that you provide must not require permissions to download.

Unreal Engine Project Technical Requirements

• The Content directory must contain a single Pack directory (unless pre-approved by the Fab team) and have the same name as the project.
• You must name the highest-level directories in the Pack directory to indicate the type of assets they contain, or to indicate the specific assets they contain.
• You must put assets inside directories with names appropriate to the asset type.
• The project must not contain any unused directories or assets.
• You must clean up all Redirectors.
• Directory and file naming must be in English, alphanumeric, and consistent throughout the project. Directory and file names must also describe what the assets are.
• If needed, you must provide either linked or in-editor documentation and tutorials.
• In .uproject, disable any unused plugins.

Maps

Maps are levels in a game product. Your maps must follow the guidelines in this section.

Unreal Engine documentation: Unreal Engine-Levels in Unreal Engine.

Overview Maps

All products that have a visual component must contain an overview map that has all the products laid out.

The following product categories have visual components, and therefore must include an overview map:

• 2D Assets (if the product contains functioning UI elements or animated sprites)
• Animations
• Architectural Visualization
• Characters
• Environments
• Materials
• Props
• Textures (if the product contains materials, functioning UI elements, or animated sprites)
• Visual Effects
• Weapons

Demo Map

You can include as many demo maps as you like, as long as they are relevant and serve a purpose.

The following product categories must include at least one demo map:

• Blueprints (if the product has Blueprint elements that can be included in a demo)
• Environments

Technical Requirements for Maps

• You must build lighting on all maps.
• Your maps must generate no errors or consequential warnings.
• Your maps must have no Z-fighting or overlapping polygons.

Unreal Engine Content Guidelines

The following guidelines apply to any Unreal Engine projects that you upload to Fab.

General

• Overall project size (with Saved and Intermediate folders removed) cannot exceed 15 GB before you zip the project. If the project exceeds this limit, contact Fab Support to discuss options.

Nanite

• Minimum Content:
  • All assets must meet the minimum content for the product type that you want to distribute them in. See the sections below for details of the minimum requirements for each product type.
  • The assets must contain enough complexity in design and geometry that Nanite is properly utilized. In other words, Fab does not accept simplistic unoptimized assets as Nanite assets.
• Additional Technical Guidelines:
  • Only Unreal Engine 5.0+ products can support Nanite.
  • You must enable Nanite by default for any meshes that you intend to support Nanite.

Lumen

• Minimum Content:
  • All assets must meet the minimum content for the product type that you want to distribute them in. See the sections below for details of the minimum requirements for each product type.
• Additional Technical Guidelines:
  • Only Unreal Engine 5.0+ products can support Lumen.

2D Assets

• Minimum Content:
  • 2D art: 25 assets.
  • 2D backgrounds: 10 backgrounds.
  • Decals: 10 decal .uassets.
  • Icons: 25 assets.
  • Landscape Brushes: 25 landscape brushes.
  • Sprite Animations: 5 to 10+ depending on complexity.
• Overview map: Required if the product contains functioning UI elements or game-ready animated sprites. Otherwise not required.
• Demo map: Not required.

3D Models

Props

• Minimum Content:
  • Realistic and photogrammetry: At least 5 unique assets.
  • Low poly/simple stylized: Approximately 25 unique assets depending on complexity.
  • Firearms: At least 1 high-quality firearms asset with all expected moving parts rigged and a full set of animations.
  • Vehicle Static Meshes: At least 5 unique vehicle meshes that include an interior and exterior.
  • Vehicle Skeletal Meshes (no Blueprints): At least 1 high-quality vehicle skeletal mesh with both an interior and exterior that is correctly rigged.
• Overview Map: Required.
• Demo Map: Not required.

Characters

• Minimum content:
  • At least 1 high-quality game-ready full character model (or 5 "arms only" characters for first person) that is rigged to the Epic Skeleton, includes a full Control Rig, or includes a full custom animation set.
    • Rigged to the Epic Skeleton: The product must include the Third Person Template demo animations and have those animations laid out in the Overview Map. This is for testing purposes and proof that the character is rigged to the Epic Skeleton appropriately. The skeleton must be in A-pose, with no bones moved or renamed (additional child bones or sockets are allowed but must be documented on the product page), and the IK bones must be included and not grayed out.
    • Not rigged to the Epic Skeleton: The product must include a full set of animations with the bare minimum of idle, jump cycle, walk, and run.
      • If it makes sense with the nature of the character to not include a jump or walk animation, this can be accommodated. For example, a large dinosaur would not be required to have a jump animation.
      • If the nature of the character indicates that it should have additional animations or you want to market the character for a specific genre where certain additional animations are expected, then it must also contain those animations. For example, a warrior character with a sword and shield would be expected to have attack and block animations.

    Simple low-poly assets might increase the minimum requirement.

• Overview Map: Required.
• Demo Map: Not required.

Animations

• Minimum Content:
  • At least 10+ unique animations.
• The product page must contain some way to preview the animations.
• Overview Map: Required.
• Demo Map: Not required.

If your project is meant to be used with MetaHumans, it is subject to the additional guidelines listed in the MetaHumans: Clothing, accessories, animations, and morph targets for MetaHuman characters section on this page.

Audio

Music

• Minimum Content: At least 5 tracks.
• The product page must contain a way for Fab users to listen to samples of the music.
• Overview Map: Not required.
• Demo Map: Not required.

Sound Effects

• Minimum Content:
  • Standard Sound Effects: Approximately 20+ high-quality sounds.
  • Ambient Sounds: At least 10 tracks.
• The product page must contain a way for Fab users to listen to samples of the sound effects.
• Overview Map: Not required.
• Demo Map: Not required.

MetaSounds

• Minimum Content: This is highly dependent on the complexity of the MetaSounds, but each product must give value to users beyond that of simple tutorials or documentation. It must provide significant utility not available in existing engine patches.
  • Must contain one or both of the following asset types:
    • UMetaSoundSource
    • UMetaSoundPatch
• You must include thorough documentation in at least one of the following formats. The documentation must provide all expected information on setup and usage.
  • Video
  • Written
  • Graph comments
  • In-level text/walkthrough.
  • In-editor Unreal Engine tutorials
• Overview Map: Not required.
• Demo Map: Not required.
• Additional Technical Guidelines:
  • Only Unreal Engine 5.0+ products can support MetaSounds.
  • MetaSound (Source or Patch) inputs must have comments describing their usage.
  • MetaSound Source Presets must be organized to make clear the derived MetaSound Source and Preset.
  • MetaSound details must contain author, display name, and description.

Education and Tutorials

• Minimum Content: Evaluated per product, based on functionality.
• You must include thorough documentation in at least one of the following formats. The documentation must provide all expected information on setup and usage.
  • Video
  • Written
  • Blueprint comments
  • In-level text/walkthrough.
  • In-editor Unreal Engine tutorials
• Overview Map: Not required.
• Demo Map: Not required.

Environments

A full level environment that is completely game ready.

• Minimum Content:
  • 1 full environment evaluated per product.
• Overview Map: Required.
• Demo Map: Required.

Game Systems and Game Templates

• Minimum Content: Evaluated per product, based on functionality.
• You must include thorough documentation in at least one of the following formats. The documentation must provide all expected information on setup and usage:
  • Video
  • Written
  • Blueprint comments
  • In-level text/walkthrough.
  • In-editor Unreal Engine tutorials
• Overview Map: Not required.
• Demo Map: Required, unless the product only contains functions that are well documented.

HDRI

• Minimum Content:
  • 5 unique skyboxes
• Overview Map: Required.
• Demo Map: Not required.

Materials & Textures

• Minimum Content:
  • 1 unique material.
• Overview Map: Required.
• Demo Map: Not required.

Smart Assets

• Minimum Content: This is highly dependent on the complexity of the Blueprints themselves and if any tutorial content exists that covers all or most of the product's functionality.
  • 1 unique asset.
    • Driveable Vehicles: At least 1 high-quality driveable vehicle.

    • Firearms: At least 1 high quality weapon asset with all expected moving parts rigged and animated.

      If the vehicle is not rigged and driveable, you must submit your product under the 3D Assets category and follow the minimum guidelines for that section.

• You must include thorough documentation in at least one of the following formats. The documentation must provide all expected information on setup and usage.
  • Video
  • Written
  • Blueprint comments
  • In-level text/walkthrough.
  • In-editor Unreal Engine tutorials
• Overview Map: Not required.
• Demo Map: Required, unless the product only contains functions that are well documented.

Tools & Plugins

• Minimum Content: evaluated per product based on functionality.
• You must include thorough documentation.
• Overview Map: Not required.
• Demo Map: Not required, unless the product has elements that can be demonstrated.
• Blueprint Technical Guidelines:
  • Blueprints must be clean and not purposefully confusing.
  • Functions, variables, and events must use names that reflect intended purpose.
  • No loose Blueprint nodes unless for example or tutorial purposes.
  • Blueprints must not generate errors or consequential warnings.

User Interfaces (UI)

• Minimum Content:
  • 25 assets
  • 1 complete UI Blueprint system
• Overview Map: Not required, unless the product contains functioning UI elements or game-ready animated sprites.
• Demo Map: Not required.

Niagara VFX

High-quality particle systems created with Niagara.

• Minimum Content:
  • 1 unique asset.
• The product page must contain a video that showcases the effects.
• Overview Map: Required.
• Demo Map: Not required.

MetaHuman

Clothing, accessories, animations, and morph targets for MetaHuman digital characters.

You cannot include any MetaHuman characters or heads inside any Fab product. You can include the MetaHuman skeletal rig, but you cannot create the base character (if you include one) with MetaHuman in any way.

• Minimum Content:
  • All assets must meet the minimum content for the category that they are being distributed in and be ‘MetaHumans quality’.
  • If you include support for additional body types and want to have fewer assets per product, the Fab team will review this on a per-request basis, and work with you to find the appropriate number of assets for the product.
• Additional Technical Guidelines:
  • Do not use the term 'MetaHuman' in your product title.
  • You can use MetaHumans in the product images, if the following apply:
    • The images are rendered in Unreal Engine.
    • The images all have a clear disclaimer that the character is not included in the product.
  • You can mention 'MetaHuman' in the product's Short Description, Long Description, and Technical Information fields.
  • You can tag your products with a 'MetaHuman' tag.
  • In the product's Technical Information field, you must state exactly which combinations of character attributes your clothing supports. To do this, add the following disclaimer to the template: * MetaHuman Skeleton Support: Yes
    • Body Types Supported:
      • Tall/Masculine/Medium
      • Tall/Feminine/Medium
      • (Continue the list to cover all Body Types your product supports)
  • For functional testing during the review process, include a download link to a version of the project that has imported MetaHuman characters (one for each body type your product supports).

Unity Project Format

If your product is a Unity project, then it must follow the technical guidelines in this section.

General

• The project must meet all the relevant requirements in the Unity Asset Store Submission Guidelines.
• The project must be in a published state on the Unity Asset Store.
• The project must be submitted for publication by the same publisher on the Unity Asset Store and Fab.

Files

• The Unity Files that you submit to Fab must be approximately the same files hosted on the Unity Asset Store.
• Any required dependencies must be clearly stated in the product’s description.
• If the product is dependent on content not hosted on Fab (such as on GitHub, Google Drive, or Dropbox), then you must include links to this content on the product page.