Core Nfc

CoreNFC

Read and write NFC tags on iPhone using CoreNFC. Supports NDEF tag reader sessions, native ISO 7816/15693/FeliCa/MIFARE tag communication, and background tag reading.

Contents

• Setup & Entitlements
• NDEF Reader Session
• Tag Reader Session & Writing
• NDEF Message Construction
• Background Tag Reading
• Common Mistakes
• Review Checklist
• References

Setup & Entitlements

1. Enable Near Field Communication Tag Reading capability in Xcode.
2. Add NFCReaderUsageDescription to Info.plist.
3. Configure the entitlement com.apple.developer.nfc.readersession.formats with array value ["TAG"] (do not use legacy NDEF).
4. For ISO 7816 tags, add application identifiers to com.apple.developer.nfc.readersession.iso7816.select-identifiers.
5. For FeliCa tags, specify exact system codes in com.apple.developer.nfc.readersession.felica.systemcodes (no wildcards).

Always verify NFCNDEFReaderSession.readingAvailable before presenting NFC UI.

NDEF Reader Session

Read NDEF tags using NFCNDEFReaderSession:

import CoreNFC

final class NFCReader: NSObject, NFCNDEFReaderSessionDelegate {
    var session: NFCNDEFReaderSession?

    func beginScan() {
        guard NFCNDEFReaderSession.readingAvailable else { return }
        session = NFCNDEFReaderSession(delegate: self, queue: nil, invalidateAfterFirstRead: true)
        session?.alertMessage = "Hold iPhone near NFC tag."
        session?.begin()
    }

    func readerSession(_ session: NFCNDEFReaderSession, didDetectNDEFs messages: [NFCNDEFMessage]) {
        for message in messages {
            for record in message.records {
                // Process payload
            }
        }
    }

    func readerSession(_ session: NFCNDEFReaderSession, didInvalidateWithError error: Error) {
        // Handle session timeout, cancellation, or hardware error
    }
}

Tag Reader Session & Writing

Connect to tags and write NDEF messages using NFCTagReaderSession:

func tagReaderSession(_ session: NFCTagReaderSession, didDetect tags: [NFCTag]) {
    guard let tag = tags.first else { return }

    session.connect(to: tag) { error in
        guard error == nil else { session.invalidate(errorMessage: "Connection failed"); return }

        guard case let .ndef(ndefTag) = tag else { return }
        ndefTag.queryNDEFStatus { status, capacity, error in
            guard status == .readWrite else { return }

            let payload = NFCNDEFPayload.wellKnownTypeURIPayload(url: URL(string: "https://example.com")!)!
            let message = NFCNDEFMessage(records: [payload])

            ndefTag.writeNDEF(message) { error in
                if error == nil {
                    session.alertMessage = "Write successful!"
                    session.invalidate()
                }
            }
        }
    }
}

NDEF Message Construction

Construct standardized NDEF payloads:

// URI Payload
let uriPayload = NFCNDEFPayload.wellKnownTypeURIPayload(url: destinationURL)!

// Text Payload
let textPayload = NFCNDEFPayload.wellKnownTypeTextPayload(string: "Device-101", locale: Locale(identifier: "en"))!

let message = NFCNDEFMessage(records: [uriPayload, textPayload])

Background Tag Reading

Supported iPhones continuously scan for NDEF tags containing URL payloads when the screen is on:

• Universal links open the app directly without showing an NFC scanner UI.
• Handle background URLs via standard SwiftUI .onOpenURL or UIKit scene(_:openURLContexts:).

Common Mistakes

• Using legacy NDEF entitlement value: Use TAG in com.apple.developer.nfc.readersession.formats.
• Failing to invalidate session on success: The system NFC alert stays visible until session.invalidate() is explicitly called.
• Calling NFC APIs without checking availability: Crashes or throws on unsupported hardware or simulator targets.
• Overlooking session timeout: Sessions automatically time out after 60 seconds; handle NFCReaderError.readerSessionInvalidationErrorSessionTimeout.
• Writing to read-only tags: Always query ndefTag.queryNDEFStatus and verify .readWrite status before attempting writes.

Review Checklist

• NFCReaderUsageDescription configured in Info.plist
• com.apple.developer.nfc.readersession.formats set to ["TAG"]
• Reader availability checked before session creation
• Sessions properly invalidated upon successful read/write
• Errors handled for user cancellation and timeout

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