core-nfc

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Documentation

SKILL.md

Read and write NFC tags using CoreNFC. Use when scanning NDEF tags, reading ISO7816/ISO15693/FeliCa/MIFARE tags, writing NDEF messages, handling NFC session lifecycle, configuring NFC entitlements, or implementing background tag reading in iOS apps.

npx skills add dpearson2699/swift-ios-skills --skill core-nfc

Documentation

SKILL.mdView source

CoreNFC

Read and write NFC tags on iPhone using the CoreNFC framework. Covers NDEF reader sessions, tag reader sessions, NDEF message construction, entitlements, and background tag reading.

Setup
NDEF Reader Session
Tag Reader Session
Writing NDEF Messages
NDEF Payload Types
Background Tag Reading
Common Mistakes
Review Checklist
References

Setup

Project Configuration

Add the Near Field Communication Tag Reading capability in Xcode
Add NFCReaderUsageDescription to Info.plist with a user-facing reason string
Add the com.apple.developer.nfc.readersession.formats entitlement with the current TAG value; do not add legacy NDEF
For ISO 7816 tags, add supported application identifiers to com.apple.developer.nfc.readersession.iso7816.select-identifiers in Info.plist
For FeliCa tags, add supported system codes to com.apple.developer.nfc.readersession.felica.systemcodes; do not use wildcard system codes

Device Requirements

NFC reading requires iPhone 7 or later. Always check for reader session availability before creating NFC UI or sessions. Use the concrete reader session type you are about to create.

import CoreNFC
 
guard NFCNDEFReaderSession.readingAvailable else {
    // Device does not support NFC or feature is restricted
    showUnsupportedMessage()
    return
}

Key Types

Type	Role
`NFCNDEFReaderSession`	Scans for NDEF-formatted tags
`NFCTagReaderSession`	Scans for ISO7816, ISO15693, FeliCa, MIFARE tags
`NFCNDEFMessage`	Collection of NDEF payload records
`NFCNDEFPayload`	Single record within an NDEF message
`NFCNDEFTag`	Protocol for interacting with an NDEF-capable tag

NDEF Reader Session

Use NFCNDEFReaderSession to read NDEF-formatted data from tags. This is the simplest path for reading standard tag content like URLs, text, and MIME data.

Reading with Tag Connection

For read-write operations, use the tag-detection delegate method to connect to individual tags:

Tag Reader Session

Use NFCTagReaderSession when you need direct access to the native tag protocol (ISO 7816, ISO 15693, FeliCa, or MIFARE).

Polling option	Tags
`.iso14443`	ISO 7816-compatible and MIFARE
`.iso15693`	ISO 15693
`.iso18092`	FeliCa

Do not use this session for payment-related AIDs. Load nfc-patterns.md for protocol-specific connection, APDU, command, and response handling.

Writing NDEF Messages

Write NDEF data to a connected tag. Always check readWrite status first.

NDEF Payload Types

Creating Common Payloads

Parsing Payload Content

Load Parsing NDEF Payload Content for the complete type-name-format switch and multi-record handling.

Background Tag Reading

On iPhone XS and later, iOS can read NFC tags in the background without opening your app. The NDEF message must contain a URI record (typeNameFormat == .nfcWellKnown, type U). If there are multiple URI records, the system uses the first one.

For app-specific routing, write a universal link to the tag and configure the Associated Domains capability for that domain. Background tag reading also supports specific system URL schemes such as web, email, SMS, telephone, FaceTime, Maps, and HomeKit setup. It does not support custom URL schemes, and the system does not route by bundle ID or arbitrary NDEF content type.

When a user taps a compatible tag, iOS displays a notification that opens your app. Handle the tag data via NSUserActivity:

Common Mistakes

DON'T: Use stale or missing NFC entitlements

Without the com.apple.developer.nfc.readersession.formats entitlement, reader sessions cannot access NFC hardware. Use the current TAG value for Core NFC reader sessions; do not copy older examples that add NDEF.

DON'T: Ignore session invalidation errors

The session invalidates for multiple reasons. Distinguishing user cancellation from real errors prevents false error alerts.

DON'T: Hold a strong reference to a stale session

Once a session is invalidated, it cannot be restarted. Nil out your reference and create a new session for the next scan.

Review Checklist

References

Extended patterns (ISO 7816 commands, multi-tag scanning, NDEF locking): references/nfc-patterns.md
Core NFC framework
NFCNDEFReaderSession
NFCTagReaderSession
NFCNDEFMessage
NFCNDEFPayload
NFCNDEFTag
NFCNDEFReaderSessionDelegate
NFCTagReaderSessionDelegate
Building an NFC Tag-Reader App
Adding Support for Background Tag Reading
Near Field Communication Tag Reader Session Formats Entitlement
ISO7816 application identifiers for NFC Tag Reader Session
ISO18092 system codes for NFC Tag Reader Session

npx skills add dpearson2699/swift-ios-skills --skill core-nfc

Documentation

SKILL.md

core-nfc | SkillBundle

import CoreNFC
 
final class NDEFReader: NSObject, NFCNDEFReaderSessionDelegate {
    private var session: NFCNDEFReaderSession?
 
    func beginScanning() {
        guard NFCNDEFReaderSession.readingAvailable else { return }
 
        session = NFCNDEFReaderSession(
            delegate: self,
            queue: nil,
            invalidateAfterFirstRead: false
        )
        session?.alertMessage = "Hold your iPhone near an NFC tag."
        session?.begin()
    }
 
    // MARK: - NFCNDEFReaderSessionDelegate
 
    func readerSessionDidBecomeActive(_ session: NFCNDEFReaderSession) {
        // Session is scanning
    }
 
    func readerSession(
        _ session: NFCNDEFReaderSession,
        didDetectNDEFs messages: [NFCNDEFMessage]
    ) {
        for message in messages {
            for record in message.records {
                processRecord(record)
            }
        }
    }
 
    func readerSession(
        _ session: NFCNDEFReaderSession,
        didInvalidateWithError error: Error
    ) {
        let nfcError = error as? NFCReaderError
        if nfcError?.code != .readerSessionInvalidationErrorFirstNDEFTagRead,
           nfcError?.code != .readerSessionInvalidationErrorUserCanceled {
            print("Session invalidated: \(error.localizedDescription)")
        }
        self.session = nil
    }
}

func readerSession(
    _ session: NFCNDEFReaderSession,
    didDetect tags: [any NFCNDEFTag]
) {
    guard let tag = tags.first else {
        session.restartPolling()
        return
    }
 
    session.connect(to: tag) { error in
        if let error {
            session.invalidate(errorMessage: "Connection failed: \(error)")
            return
        }
 
        tag.queryNDEFStatus { status, capacity, error in
            guard error == nil else {
                session.invalidate(errorMessage: "Query failed.")
                return
            }
 
            switch status {
            case .notSupported:
                session.invalidate(errorMessage: "Tag is not NDEF compliant.")
            case .readOnly:
                tag.readNDEF { message, error in
                    if let message {
                        self.processMessage(message)
                    }
                    session.invalidate()
                }
            case .readWrite:
                tag.readNDEF { message, error in
                    if let message {
                        self.processMessage(message)
                    }
                    session.alertMessage = "Tag read successfully."
                    session.invalidate()
                }
            @unknown default:
                session.invalidate()
            }
        }
    }
}

func writeToTag(
    tag: any NFCNDEFTag,
    session: NFCNDEFReaderSession,
    url: URL
) {
    tag.queryNDEFStatus { status, capacity, error in
        guard status == .readWrite else {
            session.invalidate(errorMessage: "Tag is read-only.")
            return
        }
 
        guard let payload = NFCNDEFPayload.wellKnownTypeURIPayload(
            url: url
        ) else {
            session.invalidate(errorMessage: "Invalid URL.")
            return
        }
 
        let message = NFCNDEFMessage(records: [payload])
 
        tag.writeNDEF(message) { error in
            if let error {
                session.invalidate(
                    errorMessage: "Write failed: \(error.localizedDescription)"
                )
            } else {
                session.alertMessage = "Tag written successfully."
                session.invalidate()
            }
        }
    }
}

// URL payload
let urlPayload = NFCNDEFPayload.wellKnownTypeURIPayload(
    url: URL(string: "https://example.com")!
)
 
// Text payload
let textPayload = NFCNDEFPayload.wellKnownTypeTextPayload(
    string: "Hello NFC",
    locale: Locale(identifier: "en")
)
 
// Custom payload
let customPayload = NFCNDEFPayload(
    format: .nfcExternal,
    type: "com.example:mytype".data(using: .utf8)!,
    identifier: Data(),
    payload: "custom-data".data(using: .utf8)!
)

func scene(
    _ scene: UIScene,
    continue userActivity: NSUserActivity
) {
    guard userActivity.activityType ==
        NSUserActivityTypeBrowsingWeb else { return }
 
    let message = userActivity.ndefMessagePayload
    guard message.records.first?.typeNameFormat != .empty else { return }
 
    for record in message.records {
        processRecord(record)
    }
}

// WRONG -- shows error when user cancels
func readerSession(
    _ session: NFCNDEFReaderSession,
    didInvalidateWithError error: Error
) {
    showAlert("NFC Error: \(error.localizedDescription)")
}
 
// CORRECT -- filter expected invalidation reasons
func readerSession(
    _ session: NFCNDEFReaderSession,
    didInvalidateWithError error: Error
) {
    let nfcError = error as? NFCReaderError
    switch nfcError?.code {
    case .readerSessionInvalidationErrorUserCanceled,
         .readerSessionInvalidationErrorFirstNDEFTagRead:
        break  // Normal termination
    default:
        showAlert("NFC Error: \(error.localizedDescription)")
    }
    self.session = nil
}

// WRONG -- reusing invalidated session
func scanAgain() {
    session?.begin()  // Does nothing, session is dead
}
 
// CORRECT -- create a new session
func scanAgain() {
    session = NFCNDEFReaderSession(
        delegate: self, queue: nil, invalidateAfterFirstRead: false
    )
    session?.begin()
}

core-nfc

Documentation

Documentation

CoreNFC

Contents

Setup

Project Configuration

Device Requirements

Key Types

NDEF Reader Session

Reading with Tag Connection

Tag Reader Session

Writing NDEF Messages

NDEF Payload Types

Creating Common Payloads

Parsing Payload Content

Background Tag Reading

Common Mistakes

DON'T: Use stale or missing NFC entitlements

DON'T: Ignore session invalidation errors

DON'T: Hold a strong reference to a stale session

Review Checklist

References

Documentation

core-nfc

Documentation

CoreNFC

Contents

Setup

Project Configuration

Device Requirements

Key Types

NDEF Reader Session

Reading with Tag Connection

Tag Reader Session

Writing NDEF Messages

NDEF Payload Types

Creating Common Payloads

Parsing Payload Content

Background Tag Reading

Common Mistakes

DON'T: Use stale or missing NFC entitlements

DON'T: Ignore session invalidation errors

DON'T: Hold a strong reference to a stale session

Review Checklist

References