Asset Catalog Format Reference: Types Overview

The folders in asset catalogs represent the overall asset catalog, groups of assets and other groups, and several different types of assets. Some of the asset types in a catalog work only with selected Apple platforms.

Content Types

The type of content represented by a folder is encoded in the extension for the name of the folder. For example, a folder named PosingLlamas.imageset has a type of imageset.

Table 5-1 lists the content types, folder name extension, and a brief description of each type.

**Table 5-1**Content types
Folder type	Extension	Description
App Icon Type	`.appiconset`	The various sizes of the icon for an iOS or watchOS app. Children are `.png` files.
AR Reference Image	`.arimageset`	An image file for an `ARReferenceImage`. Supported file formats include HEIF (High Efficiency Image Format), JPEG, PNG, and TIFF.
AR Resource Group	`.arresourcegroup`	A group of reference images for ARKit. Children are AR Reference Image folders.
Brand Assets Type	`.brandassets`	The layered app icons and top shelf image for your app. Children are image stacks and image sets.
Catalog Type	`.xcassets`	The top level folder for the asset catalog. Children are any valid asset type except Catalog.
Cube Texture Type	`.cubetextureset`	A 3D texture mapped onto a cube. Children are `.mipmapset` folders.
Data Set Type	`.dataset`	Used to include arbitrary app data. Children are files in any format except binary executable code.
GameCenter Dashboard Image Set Type	`.gcdashboardimage`	Images for the logos in a GameCenter dashboard. Children are image sets.
GameCenter Leaderboard Type	`.gcleaderboard`	Background image stack for a GameCenter leaderboard. Children are image stacks.
GameCenter Leaderboard Set Type	`.gcleaderboardset`	Background image stack for a GameCenter leaderboard set. Children are image stacks.
Group Type	None. No period (.) can appear in the name of the group.	A group of other elements. Children are any valid asset type except Catalog.
Icon Set Type	`.iconset`	A replica of the `.iconset` format for OS X apps. Children are `.png` files.
Image Set Type	`.imageset`	An image used for `UIImage`, `NSImage`, user interface controls, and other objects using images. Children are `HEIF`(High Efficiency Image Format), `.png`, `.jpg`, `.pdf` files.
Image Stack Type	`.imagestack`	A set of layered images combined to enable parallax. Children are image stack layers.
Image Stack Layer Type	`.imagestacklayer`	A layer in an image stack. Children are image sets.
Launch Image Type	`.launchimage`	Support for app launch images. Children are `.png` files.
Mipmap Type	`.mipmapset`	An optimized set of texture images at different resolutions. Children are files for the different resolutions.
Named Color Type	`.colorset`	A named color. The name of the color can be used anywhere in an Xcode project.
Sprite Atlas Type	`.spriteatlas`	The image sets used for an `SKTextureAtlas` class. Children are image set asset folders.
Sticker Type	`.sticker`	A sticker for a sticker pack. Child is the image for the sticker.
Sticker Pack Type	`.stickerpack`	A pack of stickers for messaging. Children are `.stickersequence` and `.sticker` folders.
Sticker Sequence Type	`.stickersequence`	A set of images for an animated sticker. Children are the images for the animation.
Texture Type	`.textureset`	A 2D texture. Children are `.mipmapset` folders.
Watch Complications Type	`.complicationset`	The image sets used for the different types of watch complications. Children are image set folders.

Contents.json File

The Contents.json file specifies metadata for the asset catalog, attributes for a folder type, and attributes for asset files. Table 5-2 shows whether a Contents.json file is required, optional, or not used for each folder type.

**Table 5-2**`Contents.json` file required
Folder type	`Contents.json`
App Icon Type	Required
Brand Assets Type	Required
Catalog Type	Optional
Cube Texture Type	Required
Data Set Type	Required
GameCenter Dashboard Image Set Type	Optional
GameCenter Leaderboard Type	Optional
GameCenter Leaderboard Set Type	Optional
Group Type	Optional
Icon Set Type	None
Image Set Type	Required
Image Stack Type	Required
Image Stack Layer Type	Optional
Launch Image Type	Required
Mipmap Type	Required
Sprite Atlas Type	Optional
Sticker Type	Required
Sticker Pack Type	Required
Sticker Sequence Type	Required
Texture Type	Required
Watch Complications Type	Required

Platform Types

Table 5-3 shows the valid platforms for each folder type.

**Table 5-3**Folder type platforms
Element	iOS	OS X	tvOS	watchOS
App Icon Type	✓	–	–	✓
Brand Assets Type	–	–	✓	–
Catalog Type	✓	✓	✓	✓
Cube Texture Type	✓	✓	✓	✓
Data Set Type	✓	✓	✓	✓
GameCenter Dashboard Image Set Type	–	–	✓	–
GameCenter Leaderboard Type	–	–	✓	–
GameCenter Leaderboard Set Type	–	–	✓	–
Group Type	✓	✓	✓	✓
Icon Set Type	–	✓	–	–
Image Set Type	✓	✓	✓	✓
Image Stack Type	–	–	✓	–
Image Stack Layer Type	–	–	✓	–
Launch Image Type	✓	–	✓	–
Mipmap Type	✓	✓	✓	–
Sprite Atlas Type	✓	✓	✓	–
Sticker Type	✓	✓	✓	✓
Sticker Pack Type	✓	✓	✓	✓
Sticker Sequence Type	✓	✓	✓	✓
Texture Type	✓	✓	✓	✓
Watch Complications Type	–	–	–	✓