---
title: Uniform Type Identifiers
framework: Uniform Type Identifiers
role: collection
role_heading: Framework
platforms: [iOS 14.0+, iPadOS 14.0+, Mac Catalyst 14.0+, macOS 11.0+, tvOS 14.0+, visionOS 1.0+, watchOS 7.0+]
path: uniformtypeidentifiers
---

# Uniform Type Identifiers

Provide uniform type identifiers that describe file types for storage or transfer.

## Overview

Overview The Uniform Type Identifiers framework provides a collection of common types that map to MIME and file types. Use these types in your project to describe the file types in your app. These descriptions help the system properly handle file storage formats or in-memory data for transfer — for example, transferring data to or from the pasteboard. The identifier types can also identify other resources, such as directories, volumes, or packages. Explicitly specify relationships between types by marking them as subtypes of other types. For example, the type UTTypePNG has the identifier public.png and is a subtype of UTTypeImage (public.image). UTTypeImage is in turn a subtype of both of the following: UTTypeContent (public.content), which implies the type can be a document UTTypeData (public.data), which implies the type is representable as a byte stream note: UTTypeData also conforms to UTTypeItem (public.item), which is a generic base type for most items in a file system, such as files or directories.

## Topics

### Essentials

- [Defining file and data types for your app](uniformtypeidentifiers/defining-file-and-data-types-for-your-app.md)
- [System-declared uniform type identifiers](uniformtypeidentifiers/system-declared-uniform-type-identifiers.md)

### Uniform type identifiers

- [UTType](uniformtypeidentifiers/uttype-swift.struct.md)
- [UTTagClass](uniformtypeidentifiers/uttagclass.md)
- [UTTypeReference](uniformtypeidentifiers/uttypereference.md)

### Reference

- [UniformTypeIdentifiers Constants](uniformtypeidentifiers/uniformtypeidentifiers-constants.md)