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. 

Use this page as a guide when uploading assets for your listing. To learn more about creating a listing, see Publishing Assets for Sale

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 when creating a listing. 

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.

Media Gallery Videos

The requirements for each media gallery video are as follows:

• Resolution: 1920 x 1080

• Maximum file size: 300MB

• File format: MP4, MOV, or WEBM

Unreal Engine Project Format

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

To upload your Unreal Engine files, you must provide a Project File Link to a hosting website (such as Google Drive, Dropbox, or OneDrive). These files must be available for download and not require login information. If the files hosted at the Project File Link have a password or encryption key, you need to provide this in the Version Notes for that Project Version.

The Project File Link must host the download of a zip archive that includes only one Unreal Engine project or plugin. These files need to be available until the product has gone live.

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:  1 unique model that must be distributed as the Asset Pack Distribution Method. Otherwise, 5 unique models are recommended.

  • 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:

  • 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 recommendation.

• Overview Map: Required.

• Demo Map: Not required.

Animation

• 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.

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.

Unreal Editor for Fortnite (UEFN) Content Guidelines

The following guidelines apply to any Unreal Editor for Fortnite (UEFN) projects that you upload to Fab.

Your project must meet the following standards.

Files

Project File

Upload your project file, (.uefnproject), as a .zip archive. Each archive must contain exactly one UEFN project.

Script Files

You must not include python script files (.py).

Content

The sections below describe the technical standards your project must meet.

General Requirements

Every UEFN product must meet the following requirements:

• Meet the content requirements for your product type, as described in the Fab Technical Requirements, and the general content requirements from the Fab Distribution Agreement.

• Scale all assets in the product correctly relative to each other, and orient them along the same direction vector with the Z axis up.

• Compile cleanly, including Verse, and pass UEFN validation with no errors and no consequential warnings before you publish.

• Clean up all redirectors. To fix up all redirectors in a content folder, in the Content Browser, right-click the folder and click Update Redirector References.

• You must declare whether your product includes, uses, depends on, or distributes third-party software of any kind.

• Third-party software means any file from a source other than you or Epic Games. This includes, but is not limited to, fonts, graphics, sounds, APIs, content, source code, and compiled libraries.

On initial submission, Epic Games reviews your product to confirm that it functions in the current live UEFN release as advertised.

Levels

If your project contains assets or functionality that appear in the UEFN 3D viewport, include a level that demonstrates them.

Levels must have no z-fighting and no unreasonably overlapping polygons.

Entities and Prefab Composition

Apply best practice when creating entities and prefabs, including the following:

• Use the standard methods provided in Verse to traverse the Scene Graph hierarchy.

• Avoid repeated wide scans on the Scene Graph hierarchy during active gameplay.

• Target Scene Events as narrowly as possible. Avoid broadcasting events from high levels of the hierarchy.

• In your prefab composition, use a clear separation of responsibilities. For example, the parent Verse Component manages the high-level state and interaction, while child entities provide the specific visual and auditory effects.

For more information see: Scene Graph Best Practices.

2D Assets

Textures must meet the following requirements:

• Provide textures at their highest resolution, or at the resolution appropriate for their intended use. You can include multiple resolutions of the same texture.

• Where applicable, make both dimensions of each texture a power of 2 (for example, 1024x512 or 1024x4096).

• Keep the maximum size in either dimension at 8192 or below. We recommend 4096 or less.

3D Assets

All meshes must meet the following requirements:

• No material defects and no visible seams.

• Proper collision, where applicable.

• Proper use of LODs. State in your product description which LODs your project includes, even if it includes none.

If you advertise your assets as modular, they must also meet the following requirements:

• Place pivot points so that meshes assemble smoothly.

• Make meshes snap together cleanly on a grid.

Animations

• Animations must be clean, consistent, and visually function as intended for their purpose.

• Any skeletal mesh that’s not rigged to the MetaHuman skeleton must ship with a custom, relatively-scaled skeleton and its animations, or with a full Control Rig.

Characters

Skeletal meshes must meet the following requirements:

• Scale meshes to the MetaHuman skeleton so that they import into a new project at the correct size.

• Give joints the expected range of motion, with no visual defects.

• Rig humanoid meshes to the MetaHuman skeleton. If you prefer a custom, relatively scaled skeleton, distribute all necessary animations with it.

• Use the same bone names.

• Leave IK joints unweighted and in the same place in the hierarchy.

• Leave joint orientations unchanged.

• Document any additional bones or modifications to the skeleton, and make that documentation available on the product page.

• Physics Assets must properly cover skeletal meshes where applicable, and should yield results appropriate to the product's intended use when simulated in the Physics Asset Editor.

Materials

Use material instances wherever possible.

Visual Effects

Emitter names must be accurate and relevant to what the emitter does. Do not name an emitter “Particle Emitter” unless it is the only emitter in that particle system.

Audio

Audio files must meet the following requirements:

• Import audio into the engine as .wav files.

• Provide audio at the highest quality possible, with no unintended hitching or distortion.

Entities That Include Verse Components

Check all entities that include Verse components and NPCs that use behavior scripts. They must generate no errors and no consequential warnings. More information:

• Creating Your Own Component using Verse

• AI and NPCs

Verse Coding Standards

Verse code must meet the following requirements:

• All Verse code must compile.

• All Verse asset references must be error free.

Follow the recommended standards for writing consistent Verse code that’s easy to maintain. For more information see: Verse Code Style Guide.

Naming Conventions

Name folders and files so that another person can understand your project. Follow these rules:

• Keep naming accurate and consistent within the context of the project.

• Do not give folders or files vague names such as “Assets” or “NewFolder”.

• Use only English alphanumeric characters and underscores.

Project Structure

Organize your project folders as follows:

• Remove unused folders.

• Sort assets into folders by asset type, or into specific sets of related assets.

• Keep every asset file path to 140 characters or less, including the name of the top-level folder.

Documentation

If your product requires particular knowledge to set up or use, you must include, distribute, or direct buyers to free documentation. That documentation must cover implementation, application, and modification of the product. It must also tell buyers how to download, install, and integrate any required third-party software that you cannot redistribute in the product files.

Your documentation must meet the following requirements:

• Take the form of a web-based guide, a .txt or .pdf file, or a video.

• Write your documentation in English. You can also provide translated versions.

• Use download links that do not start the download automatically.

MetaHuman

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

• Minimum Content:

  • All assets must meet the minimum content for the category that you distribute them in and and meet the quality standards for MetaHumans.

  • 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:

  • You can mention “MetaHuman” in the name or description of your products, as long as it’s not confusing for the users. Such use should not imply it is Epic’s product (or developed in collaboration with Epic), but should rather indicate that the product is intended to work with MetaHuman. Examples of use that should generally be allowed: “Animation grid for MetaHuman” and “MetaHuman-compatibile clothing”.

  • You can tag your products with a 'MetaHuman' tag.

  • MetaHuman .mhpkg files should be no greater than 1.5 GB

  • MetaHuman clothing files should have materials applied

  • Zipped files for .mhpkg formats should not be nested (no zipped files within one another)

  • 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).

Python Scripts

You can use python scripts in your Unreal Engine projects and plugins as long as they follow these requirements for where they are located. 

• Third-party python code directory path: Content/Python/Lib/site-packages/. This helps distinguish between proprietary project code and external dependencies, which can be subject to different licensing terms and maintenance practices.

• Plugin Python code: Content/Python. This ensures that the code is discoverable by the Unreal Editor, and managed consistently with other in-project assets.

When submitting Python plugins, make sure to follow these best practices:

• Ensure that all third-party Python code complies with licensing requirements and is clearly documented within your submission.

• Do not place Python files outside of directories listed above.

• Make sure scripts are properly commented and organized. This is so that other developers and Fab reviewers can understand and maintain the scripts as needed.

• Don't include hardcoded paths or dependencies that could break outside of your local environment.

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.

• If you published your product in the Unity Asset Store, you must include the link when submitting the Fab listing.

Files

• The Unity Files that you submit to Fab must be approximately the same files hosted on the Unity Asset Store, when applicable.

• 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.