Speech Recognition
Transcribe live and pre-recorded audio to text using Apple's Speech framework.
Covers
SFSpeechRecognizer
(iOS 10+) and the new
SpeechAnalyzer
API (iOS 26+).
Contents
SpeechAnalyzer (iOS 26+)
SFSpeechRecognizer Setup
Authorization
Live Microphone Transcription
Pre-Recorded Audio File Recognition
On-Device vs Server Recognition
Handling Results
Common Mistakes
Review Checklist
References
SpeechAnalyzer (iOS 26+)
SpeechAnalyzer
is an actor-based API introduced in iOS 26 that replaces
SFSpeechRecognizer
for new projects. It uses Swift concurrency,
AsyncSequence
for results, and supports modular analysis via
SpeechTranscriber
.
Basic transcription with SpeechAnalyzer
import
Speech
// 1. Create a transcriber module
guard
let
locale
=
SpeechTranscriber
.
supportedLocale
(
equivalentTo
:
Locale
.
current
)
else
{
return
}
let
transcriber
=
SpeechTranscriber
(
locale
:
locale
,
preset
:
.
offlineTranscription
)
// 2. Ensure assets are installed
if
let
request
=
try
await
AssetInventory
.
assetInstallationRequest
(
supporting
:
[
transcriber
]
)
{
try
await
request
.
downloadAndInstall
(
)
}
// 3. Create input stream and analyzer
let
(
inputSequence
,
inputBuilder
)
=
AsyncStream
.
makeStream
(
of
:
AnalyzerInput
.
self
)
let
audioFormat
=
await
SpeechAnalyzer
.
bestAvailableAudioFormat
(
compatibleWith
:
[
transcriber
]
)
let
analyzer
=
SpeechAnalyzer
(
modules
:
[
transcriber
]
)
// 4. Feed audio buffers (from AVAudioEngine or file)
Task
{
// Append PCM buffers converted to audioFormat
let
pcmBuffer
:
AVAudioPCMBuffer
=
// ... your audio buffer
inputBuilder
.
yield
(
AnalyzerInput
(
buffer
:
pcmBuffer
)
)
inputBuilder
.
finish
(
)
}
// 5. Consume results
Task
{
for
try
await
result
in
transcriber
.
results
{
let
text
=
String
(
result
.
text
.
characters
)
print
(
text
)
}
}
// 6. Run analysis
let
lastSampleTime
=
try
await
analyzer
.
analyzeSequence
(
inputSequence
)
// 7. Finalize
if
let
lastSampleTime
{
try
await
analyzer
.
finalizeAndFinish
(
through
:
lastSampleTime
)
}
else
{
try
analyzer
.
cancelAndFinishNow
(
)
}
Transcribing an audio file with SpeechAnalyzer
let
transcriber
=
SpeechTranscriber
(
locale
:
locale
,
preset
:
.
offlineTranscription
)
let
audioFile
=
try
AVAudioFile
(
forReading
:
fileURL
)
let
analyzer
=
SpeechAnalyzer
(
inputAudioFile
:
audioFile
,
modules
:
[
transcriber
]
,
finishAfterFile
:
true
)
for
try
await
result
in
transcriber
.
results
{
print
(
String
(
result
.
text
.
characters
)
)
}
Key differences from SFSpeechRecognizer
Feature
SFSpeechRecognizer
SpeechAnalyzer
Concurrency
Callbacks/delegates
async/await + AsyncSequence
Type
class
actor
Modules
Monolithic
Composable (
SpeechTranscriber
,
SpeechDetector
)
Audio input
append(_:)
on request
AsyncStream
available
( iOS 17 , * ) { micStatus = await AVAudioApplication . requestRecordPermission ( ) } else { micStatus = await withCheckedContinuation { continuation in AVAudioSession . sharedInstance ( ) . requestRecordPermission { granted in continuation . resume ( returning : granted ) } } } return micStatus } Live Microphone Transcription The standard pattern: AVAudioEngine captures microphone audio → buffers are appended to SFSpeechAudioBufferRecognitionRequest → results stream in. import Speech import AVFoundation final class LiveTranscriber { private let recognizer = SFSpeechRecognizer ( locale : Locale ( identifier : "en-US" ) ) ! private let audioEngine = AVAudioEngine ( ) private var recognitionRequest : SFSpeechAudioBufferRecognitionRequest ? private var recognitionTask : SFSpeechRecognitionTask ? func startTranscribing ( ) throws { // Cancel any in-progress task recognitionTask ? . cancel ( ) recognitionTask = nil // Configure audio session let audioSession = AVAudioSession . sharedInstance ( ) try audioSession . setCategory ( . record , mode : . measurement , options : . duckOthers ) try audioSession . setActive ( true , options : . notifyOthersOnDeactivation ) // Create request let request = SFSpeechAudioBufferRecognitionRequest ( ) request . shouldReportPartialResults = true self . recognitionRequest = request // Start recognition task recognitionTask = recognizer . recognitionTask ( with : request ) { result , error in if let result { let text = result . bestTranscription . formattedString print ( "Transcription: ( text ) " ) if result . isFinal { self . stopTranscribing ( ) } } if let error { print ( "Recognition error: ( error ) " ) self . stopTranscribing ( ) } } // Install audio tap let inputNode = audioEngine . inputNode let recordingFormat = inputNode . outputFormat ( forBus : 0 ) inputNode . installTap ( onBus : 0 , bufferSize : 1024 , format : recordingFormat ) { buffer , _ in request . append ( buffer ) } audioEngine . prepare ( ) try audioEngine . start ( ) } func stopTranscribing ( ) { audioEngine . stop ( ) audioEngine . inputNode . removeTap ( onBus : 0 ) recognitionRequest ? . endAudio ( ) recognitionRequest = nil recognitionTask ? . cancel ( ) recognitionTask = nil } } Pre-Recorded Audio File Recognition Use SFSpeechURLRecognitionRequest for audio files on disk: func transcribeFile ( at url : URL ) async throws -> String { guard let recognizer = SFSpeechRecognizer ( ) , recognizer . isAvailable else { throw SpeechError . unavailable } let request = SFSpeechURLRecognitionRequest ( url : url ) request . shouldReportPartialResults = false return try await withCheckedThrowingContinuation { continuation in recognizer . recognitionTask ( with : request ) { result , error in if let error { continuation . resume ( throwing : error ) } else if let result , result . isFinal { continuation . resume ( returning : result . bestTranscription . formattedString ) } } } } On-Device vs Server Recognition On-device recognition (iOS 13+) works offline but supports fewer locales: let recognizer = SFSpeechRecognizer ( locale : Locale ( identifier : "en-US" ) ) ! // Check if on-device is supported for this locale if recognizer . supportsOnDeviceRecognition { let request = SFSpeechAudioBufferRecognitionRequest ( ) request . requiresOnDeviceRecognition = true // Force on-device } Tip: On-device recognition avoids network latency and the one-minute audio limit imposed by server-based recognition. However, accuracy may be lower and not all locales are supported. Check supportsOnDeviceRecognition before forcing on-device mode. Handling Results Partial vs final results let request = SFSpeechAudioBufferRecognitionRequest ( ) request . shouldReportPartialResults = true // default is true recognizer . recognitionTask ( with : request ) { result , error in guard let result else { return } if result . isFinal { // Final transcription — recognition is complete let final = result . bestTranscription . formattedString } else { // Partial result — may change as more audio is processed let partial = result . bestTranscription . formattedString } } Accessing alternative transcriptions and confidence recognizer . recognitionTask ( with : request ) { result , error in guard let result else { return } // Best transcription let best = result . bestTranscription // All alternatives (sorted by confidence, descending) for transcription in result . transcriptions { for segment in transcription . segments { print ( " ( segment . substring ) : ( segment . confidence ) " ) } } } Adding punctuation (iOS 16+) let request = SFSpeechAudioBufferRecognitionRequest ( ) request . addsPunctuation = true Contextual strings Improve recognition of domain-specific terms: let request = SFSpeechAudioBufferRecognitionRequest ( ) request . contextualStrings = [ "SwiftUI" , "Xcode" , "CloudKit" ] Common Mistakes Not requesting both speech and microphone authorization // ❌ DON'T: Only request speech authorization for live audio SFSpeechRecognizer . requestAuthorization { status in // Missing microphone permission — audio engine will fail self . startRecording ( ) } // ✅ DO: Request both permissions before recording SFSpeechRecognizer . requestAuthorization { status in guard status == . authorized else { return } AVAudioSession . sharedInstance ( ) . requestRecordPermission { granted in guard granted else { return } self . startRecording ( ) } } Not handling availability changes // ❌ DON'T: Assume recognizer stays available after initial check let recognizer = SFSpeechRecognizer ( ) ! // Recognition may fail if network drops or locale changes // ✅ DO: Monitor availability via delegate recognizer . delegate = self func speechRecognizer ( _ speechRecognizer : SFSpeechRecognizer , availabilityDidChange available : Bool ) { recordButton . isEnabled = available } Not stopping the audio engine when recognition ends // ❌ DON'T: Leave audio engine running after recognition finishes recognizer . recognitionTask ( with : request ) { result , error in if result ? . isFinal == true { // Audio engine still running, wasting resources and battery } } // ✅ DO: Clean up all audio resources recognizer . recognitionTask ( with : request ) { result , error in if result ? . isFinal == true || error != nil { self . audioEngine . stop ( ) self . audioEngine . inputNode . removeTap ( onBus : 0 ) self . recognitionRequest ? . endAudio ( ) self . recognitionRequest = nil } } Assuming on-device recognition is available for all locales // ❌ DON'T: Force on-device without checking support let request = SFSpeechAudioBufferRecognitionRequest ( ) request . requiresOnDeviceRecognition = true // May silently fail // ✅ DO: Check support before requiring on-device if recognizer . supportsOnDeviceRecognition { request . requiresOnDeviceRecognition = true } else { // Fall back to server-based or inform user } Not handling the one-minute recognition limit // ❌ DON'T: Start one long continuous recognition session func startRecording ( ) { // This will be cut off after ~60 seconds (server-based) } // ✅ DO: Restart recognition when approaching the limit func startRecording ( ) { // Use a timer to restart before the limit recognitionTimer = Timer . scheduledTimer ( withTimeInterval : 55 , repeats : false ) { [ weak self ] _ in self ? . restartRecognition ( ) } } Creating multiple simultaneous recognition tasks // ❌ DON'T: Start a new task without canceling the previous one func startRecording ( ) { recognitionTask = recognizer . recognitionTask ( with : request ) { ... } // Previous task is still running — undefined behavior } // ✅ DO: Cancel existing task before creating a new one func startRecording ( ) { recognitionTask ? . cancel ( ) recognitionTask = nil recognitionTask = recognizer . recognitionTask ( with : request ) { ... } } Review Checklist NSSpeechRecognitionUsageDescription is in Info.plist NSMicrophoneUsageDescription is in Info.plist (if using live audio) Authorization is requested before starting recognition SFSpeechRecognizerDelegate is set to handle availabilityDidChange Audio engine is stopped and tap removed when recognition ends recognitionRequest.endAudio() is called when done recording Previous recognitionTask is canceled before starting a new one supportsOnDeviceRecognition is checked before requiring on-device mode Partial results are handled separately from final ( isFinal ) results One-minute limit is accounted for in server-based recognition For iOS 26+: AssetInventory assets are installed before using SpeechAnalyzer For iOS 26+: SpeechTranscriber.supportedLocale(equivalentTo:) is checked References Speech framework SpeechAnalyzer SpeechTranscriber SFSpeechRecognizer SFSpeechAudioBufferRecognitionRequest SFSpeechURLRecognitionRequest SFSpeechRecognitionResult SFSpeechRecognitionRequest AssetInventory Asking Permission to Use Speech Recognition Recognizing Speech in Live Audio