AccessorySetupKit

Privacy-preserving accessory discovery and setup for Bluetooth and Wi-Fi

devices. Replaces broad Bluetooth/Wi-Fi permission prompts with a

system-provided picker that grants per-accessory access with a single tap.

Available iOS 18+ / Swift 6.3.

After setup, apps continue using CoreBluetooth and NetworkExtension for

communication. AccessorySetupKit handles only the discovery and authorization

step.

Contents

• [Setup and Entitlements](#setup-and-entitlements)

• [Discovery Descriptors](#discovery-descriptors)

• [Presenting the Picker](#presenting-the-picker)

• [Event Handling](#event-handling)

• [Bluetooth Accessories](#bluetooth-accessories)

• [Wi-Fi Accessories](#wi-fi-accessories)

• [Migration from CoreBluetooth](#migration-from-corebluetooth)

• [Common Mistakes](#common-mistakes)

• [Review Checklist](#review-checklist)

• [References](#references)

Setup and Entitlements

Info.plist Configuration

Add these keys to the app's Info.plist:

Key

Type

Purpose

NSAccessorySetupSupports

[String]

Required. Array containing Bluetooth and/or WiFi

NSAccessorySetupBluetoothServices

[String]

Service UUIDs the app discovers (Bluetooth)

NSAccessorySetupBluetoothNames

[String]

Bluetooth names or substrings to match

NSAccessorySetupBluetoothCompanyIdentifiers

[Number]

Bluetooth company identifiers

The Bluetooth-specific keys must match the values used in ASDiscoveryDescriptor.

If the app uses identifiers, names, or services not declared in Info.plist, the

app crashes at discovery time.

No Bluetooth Permission Required

When an app declares NSAccessorySetupSupports with Bluetooth, creating a

CBCentralManager no longer triggers the system Bluetooth permission dialog.

The central manager's state transitions to poweredOn only when the app has

at least one paired accessory via AccessorySetupKit.

Discovery Descriptors

ASDiscoveryDescriptor defines the matching criteria for finding accessories.

The system matches scanned results against all rules in the descriptor to

filter for the target accessory.

Bluetooth Descriptor

import AccessorySetupKit

import CoreBluetooth

var descriptor = ASDiscoveryDescriptor()

descriptor.bluetoothServiceUUID = CBUUID(string: "12345678-1234-1234-1234-123456789ABC")

descriptor.bluetoothNameSubstring = "MyDevice"

descriptor.bluetoothRange = .immediate  // Only nearby devices

A Bluetooth descriptor requires bluetoothCompanyIdentifier or

bluetoothServiceUUID, plus at least one of:

• bluetoothNameSubstring

• bluetoothManufacturerDataBlob and bluetoothManufacturerDataMask (same length)

• bluetoothServiceDataBlob and bluetoothServiceDataMask (same length)

Wi-Fi Descriptor

var descriptor = ASDiscoveryDescriptor()

descriptor.ssid = "MyAccessory-Network"

// OR use a prefix:

// descriptor.ssidPrefix = "MyAccessory-"

Supply either ssid or ssidPrefix, not both. The app crashes if both are set.

The ssidPrefix must have a non-zero length.

Bluetooth Range

Control the physical proximity required for discovery:

Value

Behavior

.default

Standard Bluetooth range

.immediate

Only accessories in close physical proximity

Support Options

Set supportedOptions on the descriptor to declare the accessory's capabilities:

descriptor.supportedOptions = [.bluetoothPairingLE, .bluetoothTransportBridging]

Option

Purpose

.bluetoothPairingLE

BLE pairing support

.bluetoothTransportBridging

Bluetooth transport bridging

.bluetoothHID

Bluetooth HID device

Presenting the Picker

Creating the Session

Create and activate an ASAccessorySession to manage discovery lifecycle:

import AccessorySetupKit

final class AccessoryManager {

    private let session = ASAccessorySession()

    func start() {

        session.activate(on: .main) { [weak self] event in

            self?.handleEvent(event)

        }

    }

    private func handleEvent(_ event: ASAccessoryEvent) {

        switch event.eventType {

        case .activated:

            // Session ready. Check session.accessories for previously paired devices.

            break

        case .accessoryAdded:

            guard let accessory = event.accessory else { return }

            handleAccessoryAdded(accessory)

        case .accessoryChanged:

            // Accessory properties changed (e.g., display name updated in Settings)

            break

        case .accessoryRemoved:

            // Accessory removed by user or app

            break

        case .invalidated:

            // Session invalidated, cannot be reused

            break

        default:

            break

        }

    }

}

Showing the Picker

Create ASPickerDisplayItem instances with a name, product image, and

discovery descriptor, then pass them to the session:

func showAccessoryPicker() {

    var descriptor = ASDiscoveryDescriptor()

    descriptor.bluetoothServiceUUID = CBUUID(string: "ABCD1234-0000-1000-8000-00805F9B34FB")

    guard let image = UIImage(named: "my-accessory") else { return }

    let item = ASPickerDisplayItem(

        name: "My Bluetooth Accessory",

        productImage: image,

        descriptor: descriptor

    )

    session.showPicker(for: [item]) { error in

        if let error {

            print("Picker failed: \(error.localizedDescription)")

        }

    }

}

The picker runs in a separate system process. It shows each matching device

as a separate item. When multiple devices match a given descriptor, the picker

creates a horizontal carousel.

Setup Options

Configure picker behavior per display item:

var item = ASPickerDisplayItem(

    name: "My Accessory",

    productImage: image,

    descriptor: descriptor

)

item.setupOptions = [.rename, .confirmAuthorization]

Option

Effect

.rename

Allow renaming the accessory during setup

.confirmAuthorization

Show authorization confirmation before setup

.finishInApp

Signal that setup continues in the app after pairing

Product Images

The picker displays images in a 180x120 point container. Best practices:

• Use high-resolution images for all screen scale factors

• Use transparent backgrounds for correct light/dark mode appearance

• Adjust transparent borders as padding to control apparent accessory size

• Test in both light and dark mode

Event Handling

Event Types

The session delivers ASAccessoryEvent objects through the event handler:

Event

When

.activated

Session is active, query session.accessories

.accessoryAdded

User selected an accessory in the picker

.accessoryChanged

Accessory properties updated (e.g., renamed)

.accessoryRemoved

Accessory removed from system

.invalidated

Session invalidated, create a new one

.migrationComplete

Migration of legacy accessories completed

.pickerDidPresent

Picker appeared on screen

.pickerDidDismiss

Picker dismissed

.pickerSetupBridging

Transport bridging setup in progress

.pickerSetupPairing

Bluetooth pairing in progress

.pickerSetupFailed

Setup failed

.pickerSetupRename

User is renaming the accessory

.accessoryDiscovered

New accessory found (custom filtering mode)

Coordinating Picker Dismissal

When the user selects an accessory, .accessoryAdded fires before

.pickerDidDismiss. To show custom setup UI after the picker closes, store the

accessory on the first event and act on it after dismissal:

private var pendingAccessory: ASAccessory?

private func handleEvent(_ event: ASAccessoryEvent) {

    switch event.eventType {

    case .accessoryAdded:

        pendingAccessory = event.accessory

    case .pickerDidDismiss:

        if let accessory = pendingAccessory {

            pendingAccessory = nil

            beginCustomSetup(accessory)

        }

    default:

        break

    }

}

Bluetooth Accessories

After an accessory is added via the picker, use CoreBluetooth to communicate.

The bluetoothIdentifier on the ASAccessory maps to a CBPeripheral.

import CoreBluetooth

func handleAccessoryAdded(_ accessory: ASAccessory) {

    guard let btIdentifier = accessory.bluetoothIdentifier else { return }

    // Create CBCentralManager — no Bluetooth permission prompt appears

    let centralManager = CBCentralManager(delegate: self, queue: nil)

    // After poweredOn, retrieve the peripheral

    let peripherals = centralManager.retrievePeripherals(

        withIdentifiers: [btIdentifier]

    )

    guard let peripheral = peripherals.first else { return }

    centralManager.connect(peripheral, options: nil)

}

Key points:

• CBCentralManager state reaches .poweredOn only when the app has paired accessories

• Scanning with scanForPeripherals(withServices:) returns only

accessories paired through AccessorySetupKit

• No NSBluetoothAlwaysUsageDescription is needed when using AccessorySetupKit

exclusively

Wi-Fi Accessories

For Wi-Fi accessories, the ssid on the ASAccessory identifies the network.

Use NEHotspotConfiguration from NetworkExtension to join it:

import NetworkExtension

func handleWiFiAccessoryAdded(_ accessory: ASAccessory) {

    guard let ssid = accessory.ssid else { return }

    let configuration = NEHotspotConfiguration(ssid: ssid)

    NEHotspotConfigurationManager.shared.apply(configuration) { error in

        if let error {

            print("Wi-Fi join failed: \(error.localizedDescription)")

        }

    }

}

Because the accessory was discovered through AccessorySetupKit, joining the

network does not trigger the standard Wi-Fi access prompt.

Migration from CoreBluetooth

Apps with existing CoreBluetooth-authorized accessories can migrate them to

AccessorySetupKit using ASMigrationDisplayItem. This is a one-time operation

that registers known accessories in the new system.

func migrateExistingAccessories() {

    guard let image = UIImage(named: "my-accessory") else { return }

    var descriptor = ASDiscoveryDescriptor()

    descriptor.bluetoothServiceUUID = CBUUID(string: "ABCD1234-0000-1000-8000-00805F9B34FB")

    let migrationItem = ASMigrationDisplayItem(

        name: "My Accessory",

        productImage: image,

        descriptor: descriptor

    )

    // Set the peripheral identifier from CoreBluetooth

    migrationItem.peripheralIdentifier = existingPeripheralUUID

    // For Wi-Fi accessories:

    // migrationItem.hotspotSSID = "MyAccessory-WiFi"

    session.showPicker(for: [migrationItem]) { error in

        if let error {

            print("Migration failed: \(error.localizedDescription)")

        }

    }

}

Migration rules:

• If showPicker contains only migration items, the system shows an

informational page instead of a discovery picker

• If migration items are mixed with regular display items, migration happens

only when a new accessory is discovered and set up

• Do not initialize CBCentralManager before migration completes — doing so

causes an error and the picker fails to appear

• The session receives .migrationComplete when migration finishes

Common Mistakes

DON'T: Omit Info.plist keys for Bluetooth discovery

The app crashes if it uses identifiers, names, or services in descriptors that

are not declared in Info.plist.

// WRONG — service UUID not in NSAccessorySetupBluetoothServices

var descriptor = ASDiscoveryDescriptor()

descriptor.bluetoothServiceUUID = CBUUID(string: "UNDECLARED-UUID")

session.showPicker(for: [item]) { _ in }  // Crash

// CORRECT — declare all UUIDs in Info.plist first

// Info.plist: NSAccessorySetupBluetoothServices = ["ABCD1234-..."]

var descriptor = ASDiscoveryDescriptor()

descriptor.bluetoothServiceUUID = CBUUID(string: "ABCD1234-...")

DON'T: Set both ssid and ssidPrefix

// WRONG — crashes at runtime

var descriptor = ASDiscoveryDescriptor()

descriptor.ssid = "MyNetwork"

descriptor.ssidPrefix = "My"  // Cannot set both

// CORRECT — use one or the other

var descriptor = ASDiscoveryDescriptor()

descriptor.ssid = "MyNetwork"

DON'T: Initialize CBCentralManager before migration

// WRONG — migration fails, picker does not appear

let central = CBCentralManager(delegate: self, queue: nil)

session.showPicker(for: [migrationItem]) { error in

    // error is non-nil

}

// CORRECT — wait for .migrationComplete before using CoreBluetooth

session.activate(on: .main) { event in

    if event.eventType == .migrationComplete {

        let central = CBCentralManager(delegate: self, queue: nil)

    }

}

DON'T: Show the picker without user intent

// WRONG — picker appears unexpectedly on app launch

override func viewDidLoad() {

    super.viewDidLoad()

    session.showPicker(for: items) { _ in }

}

// CORRECT — bind picker to a user action

@IBAction func addAccessoryTapped(_ sender: UIButton) {

    session.showPicker(for: items) { _ in }

}

DON'T: Reuse an invalidated session

// WRONG — session is dead after invalidation

session.showPicker(for: items) { _ in }  // No effect

// CORRECT — create a new session

let newSession = ASAccessorySession()

newSession.activate(on: .main) { event in

    // Handle events

}

Review Checklist

• NSAccessorySetupSupports added to Info.plist with Bluetooth and/or WiFi

• Bluetooth-specific plist keys (NSAccessorySetupBluetoothServices, NSAccessorySetupBluetoothNames, NSAccessorySetupBluetoothCompanyIdentifiers) match descriptor values

• Session activated before calling showPicker

• Event handler uses [weak self] to avoid retain cycles

• All ASAccessoryEventType cases handled, including @unknown default

• Product images use transparent backgrounds and appropriate resolution

• ssid and ssidPrefix are never set simultaneously on a descriptor

• Picker presentation tied to explicit user action, not automatic

• CBCentralManager not initialized until after migration completes (if migrating)

• bluetoothIdentifier or ssid from ASAccessory used to connect post-setup

• Invalidated sessions replaced with new instances

• Accessory removal events handled to clean up app state

References

• Extended patterns (custom filtering, batch setup, removal handling, error recovery): references/accessorysetupkit-patterns.md

• AccessorySetupKit framework

• ASAccessorySession

• ASDiscoveryDescriptor

• ASPickerDisplayItem

• ASAccessory

• ASAccessoryEvent

• ASMigrationDisplayItem

• Discovering and configuring accessories

• Setting up and authorizing a Bluetooth accessory

• Meet AccessorySetupKit — WWDC24