core-nfc

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. Targets Swift 6.2 / iOS 26+. Contents 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 tag types your app reads (e.g., NDEF , TAG ) For ISO 7816 tags, add supported application identifiers to com.apple.developer.nfc.readersession.iso7816.select-identifiers in Info.plist Device Requirements NFC reading requires iPhone 7 or later. Always check for reader session availability before presenting NFC UI. 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). final class TagReader : NSObject , NFCTagReaderSessionDelegate { private var session : NFCTagReaderSession ? func beginScanning ( ) { session = NFCTagReaderSession ( pollingOption : [ . iso14443 , . iso15693 ] , delegate : self , queue : nil ) session ? . alertMessage = "Hold your iPhone near a tag." session ? . begin ( ) } func tagReaderSessionDidBecomeActive ( _ session : 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 } switch tag { case . iso7816 ( let iso7816Tag ) : self . readISO7816 ( tag : iso7816Tag , session : session ) case . miFare ( let miFareTag ) : self . readMiFare ( tag : miFareTag , session : session ) case . iso15693 ( let iso15693Tag ) : self . readISO15693 ( tag : iso15693Tag , session : session ) case . feliCa ( let feliCaTag ) : self . readFeliCa ( tag : feliCaTag , session : session ) @unknown default : session . invalidate ( errorMessage : "Unsupported tag type." ) } } } func tagReaderSession ( _ session : NFCTagReaderSession , didInvalidateWithError error : Error ) { self . session = nil } } 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 ( ) } } } } NDEF Payload Types Creating Common Payloads // 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 ) ! ) Parsing Payload Content func processRecord ( _ record : NFCNDEFPayload ) { switch record . typeNameFormat { case . nfcWellKnown : if let url = record . wellKnownTypeURIPayload ( ) { print ( "URL: ( url ) " ) } else if let ( text , locale ) = record . wellKnownTypeTextPayload ( ) { print ( "Text ( ( locale ) ) : ( text ) " ) } case . absoluteURI : if let uri = String ( data : record . payload , encoding : . utf8 ) { print ( "Absolute URI: ( uri ) " ) } case . media : let mimeType = String ( data : record . type , encoding : . utf8 ) ?? "" print ( "MIME type: ( mimeType ) , size: ( record . payload . count ) " ) case . nfcExternal : let type = String ( data : record . type , encoding : . utf8 ) ?? "" print ( "External type: ( type ) " ) case . empty , . unknown , . unchanged : break @unknown default : break } } Background Tag Reading On iPhone XS and later, iOS can read NFC tags in the background without opening your app. To opt in: Add associated domains or universal links that match the URL on your tags Register your app for the tag's NDEF content type Include your app's bundle ID in the tag's NDEF record 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 } if let message = userActivity . ndefMessagePayload { for record in message . records { processRecord ( record ) } } } Common Mistakes DON'T: Forget the NFC entitlement Without the com.apple.developer.nfc.readersession.formats entitlement, session creation crashes at runtime. // WRONG -- entitlement not added, crashes let session = NFCNDEFReaderSession ( delegate : self , queue : nil , invalidateAfterFirstRead : true ) // CORRECT -- add entitlement in Signing & Capabilities first // Then the same code works: let session = NFCNDEFReaderSession ( delegate : self , queue : nil , invalidateAfterFirstRead : true ) DON'T: Skip the readingAvailable check Attempting to create an NFC session on an unsupported device (iPad, iPod touch, or iPhone 6s and earlier) crashes. // WRONG func scan ( ) { let session = NFCNDEFReaderSession ( delegate : self , queue : nil , invalidateAfterFirstRead : true ) session . begin ( ) } // CORRECT func scan ( ) { guard NFCNDEFReaderSession . readingAvailable else { showUnsupportedAlert ( ) return } let session = NFCNDEFReaderSession ( delegate : self , queue : nil , invalidateAfterFirstRead : true ) session . begin ( ) } DON'T: Ignore session invalidation errors The session invalidates for multiple reasons. Distinguishing user cancellation from real errors prevents false error alerts. // 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 } 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. // 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 ( ) } DON'T: Write without checking tag status Writing to a read-only tag silently fails or produces confusing errors. // WRONG -- writes without checking status tag . writeNDEF ( message ) { error in // May fail on read-only tags } // CORRECT -- check status first tag . queryNDEFStatus { status , capacity , error in guard status == . readWrite else { session . invalidate ( errorMessage : "Tag is read-only." ) return } tag . writeNDEF ( message ) { error in // Handle result } } Review Checklist NFC capability added in Signing & Capabilities NFCReaderUsageDescription set in Info.plist com.apple.developer.nfc.readersession.formats entitlement configured with correct tag types NFCNDEFReaderSession.readingAvailable checked before creating sessions Session delegate set before calling begin() Session reference set to nil after invalidation didInvalidateWithError distinguishes user cancellation from actual errors NDEF status queried before write operations Tag capacity checked before writing large messages ISO 7816 application identifiers listed in Info.plist if using NFCTagReaderSession Background tag reading configured with associated domains if needed Only one reader session active at a time 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