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.
SKILL.md
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.
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.
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
}
}
Reading with Tag Connection
For read-write operations, use the tag-detection delegate method to connect
to individual tags:
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()
}
}
}
}
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.
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()
}
}
}
}
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:
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)
}
}
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.
