The iOS app glossary

A

ActivityKit

The framework for starting and updating Live Activities. The interface itself is drawn with WidgetKit and SwiftUI. See widgets and Live Activities.

App Clip

A small part of an app that people can use without installing the whole app, opened from a link, an NFC tag or a code.

App Intents

The framework that makes an app’s actions and content available to Siri, Shortcuts, Spotlight and widgets. In iOS 27, App Intents schemas connect apps to Siri through natural language.

App preview

A short video on the App Store product page, made from footage of the app. You can add up to three, each up to 30 seconds; they autoplay muted.

App Privacy details

The answers in App Store Connect about what data an app collects, including through third-party SDKs. They become the privacy label on the product page and are required for every submission.

App Review

Apple’s review of every app, update and in-app purchase before it reaches the App Store. Apple says it reviews at least 50% of submissions in under 24 hours. See why apps get rejected.

App Review Guidelines

Apple’s rules for what the App Store accepts, numbered by section, such as 2.1 for completeness or 4.3 for spam. They change several times a year; see the latest changes.

App Store Connect

Apple’s website for managing apps: builds, metadata, screenshots, TestFlight, in-app purchases, pricing, analytics and submissions to App Review.

App Store Optimization (ASO)

Improving how an app is found and chosen on the App Store: its name, subtitle, keywords, screenshots and ratings. See the ASO checklist.

App Store Small Business Program

A program that lowers Apple’s commission to 15% for developers who earned up to 1 million USD in proceeds in the previous calendar year. Members with fewer than 2 million first-time downloads can also use Apple’s models on Private Cloud Compute at no cloud API cost.

App Tracking Transparency (ATT)

The permission an app must get before tracking people across other companies’ apps and websites. It is a separate prompt from any other consent in the app.

Apple Developer Program

The membership needed to publish on the App Store, at 99 USD per year, for an individual or an organisation. See how to publish an app.

B

Bundle ID

The unique identifier of an app, such as com.example.app. It must match the Xcode project and cannot change after a build has been uploaded.

C

CKSyncEngine

A CloudKit class, from iOS 17, that syncs an app’s own local store with CloudKit, handling scheduling, change tracking and push notifications.

CloudKit

Apple’s service for storing app data in iCloud, with a private database per person, a public database and a shared database. See CloudKit sync.

Core AI

A framework introduced in iOS 27 for running your own AI models on the device, compiled for Apple silicon, with no server and no token costs.

Core Data

Apple’s long-standing framework for storing structured data on the device. With NSPersistentCloudKitContainer it can sync through CloudKit.

Core ML

Apple’s framework, since iOS 11, for running machine learning models on the device.

Creative assets

Images and videos for the App Store product page header and search results, beyond screenshots. Guideline 2.3.14 covers them. See creative assets.

Custom product page

An extra version of an app’s product page with its own screenshots, previews and promotional text, and a unique URL. An app can have up to 70.

D

D-U-N-S Number

A nine-digit business identifier from Dun & Bradstreet. Apple uses it to verify organisations that enroll in the Developer Program.

Deployment target

The oldest iOS version an app supports. From April 2027, Apple requires uploads to target iOS 15 or later.

Device Hub

A part of Xcode 27 that brings devices and simulators together, including a resizable simulator for testing layouts.

Dynamic Island

The interactive area around the front camera on recent iPhones, where Live Activities and system alerts appear.

Dynamic Type

The iOS setting that lets people choose their text size. Apps that support it scale their text, and their layout, to match.

F

Family Sharing

Lets a subscriber share an auto-renewable subscription or a non-consumable purchase with up to five family members, if the developer turns it on.

Foundation Models framework

Apple’s Swift API, from iOS 26, for the language model behind Apple Intelligence. In iOS 27 it can also use Private Cloud Compute and other model providers. See on-device AI.

H

Human Interface Guidelines (HIG)

Apple’s design guidance for every platform: layout, typography, controls, accessibility and patterns such as onboarding and in-app purchase.

I

In-App Events

Timely events inside an app, such as a challenge or a premiere, shown on the product page, in search and on the Today tab.

In-app purchase

Apple’s system for selling digital goods inside an app, in four types: consumable, non-consumable, auto-renewable subscription and non-renewing subscription.

iPhone Duo

Apple’s iPhone with two displays and a hinge, available from 23 October 2026. Apps built with the iOS 27.1 SDK are optimised for it. See getting ready for iPhone Duo.

L

Liquid Glass

The translucent material at the heart of Apple’s design language since iOS 26, used for controls and navigation that float above content.

Live Activity

Up-to-date information about an event over minutes or hours, such as a delivery or a score, on the Lock Screen and in the Dynamic Island.

O

Offer codes

Codes that give a subscription free or at a discount for a set time, either one-time codes or custom codes such as SPRINGPROMO.

P

Phased release

Releasing an app update gradually over 7 days to people with automatic updates on, so problems show before everyone has the update.

Private Cloud Compute

Apple’s servers for running its larger models privately. Eligible small developers can use them through the Foundation Models framework at no cloud API cost.

Product page optimization

App Store testing of up to three alternate icons, screenshots or previews against the original, one test at a time, for up to 90 days.

Promotional text

Up to 170 characters above the description that can change at any time without a new version. Apple says it does not affect search ranking.

Purpose string

The sentence in an app’s Info.plist that the system shows when it asks for a permission, such as the camera. Vague purpose strings are a common review problem.

S

SDK

Software development kit. Apple sets a minimum SDK for uploads each spring: the iOS 26 SDK since April 2026, and the iOS 27 SDK from April 2027.

Sign in with Apple

Apple’s private sign-in option, which lets people hide their email address. It is the usual way to meet guideline 4.8 when an app also offers social logins.

Size classes

Compact or regular, for width and height: how iOS tells an app how much space it has. Apple’s advice is to lay out by size class, not by device.

StoreKit 2

Apple’s Swift API for in-app purchases and subscriptions, from iOS 15, with signed transactions. The original StoreKit API is deprecated as of iOS 18. See StoreKit 2 subscriptions.

Subscription group

A set of subscriptions with different levels, prices or durations, of which a person can hold only one at a time. Most apps need a single group.

Swift

Apple’s programming language for its platforms, released in 2014. It compiles to native code. See why we only build in Swift.

SwiftData

Apple’s Swift-native framework for storing app data, from iOS 17, built on Core Data and able to sync with CloudKit.

SwiftUI

Apple’s declarative framework for building interfaces in Swift, introduced in 2019. See SwiftUI vs UIKit.

T

TestFlight

Apple’s beta testing service: up to 100 internal testers from your team and up to 10,000 external testers, invited by email or a public link.

TipKit

Apple’s framework for showing short tips in context, an alternative to long onboarding tours. See onboarding best practices.

U

UIKit

Apple’s original, imperative framework for iOS interfaces. Still updated every year and often used alongside SwiftUI.

Universal links

Ordinary web links that open the right screen in an app when it is installed, and the website when it is not.

V

VoiceOver

The screen reader built into iOS. Apple’s standard controls support it automatically; custom controls need labels and traits.

W

WidgetKit

The framework for widgets on the Home Screen, Lock Screen and Today View, written in SwiftUI.

X

Xcode

Apple’s development environment for building, testing and uploading apps. It runs on the Mac; Xcode Cloud can run builds in the cloud.