---
title: Legacy Extension
framework: tvservices
role: collectionGroup
role_heading: API Collection
path: tvservices/legacy-extension
---

# Legacy Extension

Help users discover your app by providing top shelf content and a description of your tvOS app.

## Overview

Overview In iOS 12 and earlier, you provide Top Shelf information by adding a TVServices app extension to your app. Your extension returns an array describing available content for your app, and the system uses this information to update the Top Shelf. You describe your media to the operating system using TVContentItem objects. Each TVContentItem object represents either a piece of content or acts as a container for other TVContentItem objects. A content object typically includes an image and a title for tvOS to display, along with other metadata related to the content item. important: The memory limits for Top Shelf extensions are significantly lower than the memory limits imposed on tvOS apps. Performing memory-intensive operations in a Top Shelf extension, such as image editing or compositing, could push your extension beyond the high-water mark and force it to be terminated. If you must perform cpu-intensive or memory-intensive operations to generate Top Shelf content, perform those operations on a server and provide URLs to the generated resources. For more information on creating extensions, see App Extension Programming Guide. In order for tvOS to track content items, you create a unique string for each content item. You can choose your own algorithm to create these identifiers. However, any string you create should identify its content item forever; never recycle identifiers for new content. You package an identifier in a TVContentIdentifier object, which includes the string and the parent container of the item. To summarize, to provide descriptions of content to Apple TV, you must: Organize your media and app content, either as a single list or in a hierarchical model Design an algorithm or standard that supplies each content item with a unique content identifier string Create a TVContentItem object for each container or content item Add an app extension whose main class implements the TVTopShelfProvider protocol

## Topics

### Extension

- [TVTopShelfProvider](tvservices/tvtopshelfprovider.md)

### Content

- [TVContentItem](tvservices/tvcontentitem.md)
- [TVContentIdentifier](tvservices/tvcontentidentifier.md)
- [TVTopShelfImageSize(shape:style:)](tvservices/tvtopshelfimagesize(shape:style:).md)

## See Also

### Top shelf app extensions

- [Building a Full Screen Top Shelf Extension](tvservices/building-a-full-screen-top-shelf-extension.md)
- [TVTopShelfContentProvider](tvservices/tvtopshelfcontentprovider.md)