SMS autofill	Phone number hint	User consent dialog

Looking for a PIN / OTP input field? See Pinput.

Features

• SMS autofill with the SMS Retriever API and the SMS User Consent API
• Phone number hint through the Phone Number Hint API
• Credential Manager (docs):
  • get saved passwords and passkeys: getCredential
  • save a password: createPasswordCredential
  • create a passkey: createPublicKeyCredential
  • speed up the account selector on Android 14+: prepareGetCredential, getPreparedCredential
  • clear state on sign out: clearCredentialState

Platform: Android only.

Install

flutter pub add smart_auth

import 'package:smart_auth/smart_auth.dart';

final smartAuth = SmartAuth.instance;

Usage

Every method returns a SmartAuthResult: check hasData, isCanceled or read the error.

Phone number hint

Shows the user's SIM-based phone numbers as a hint. No extra permission, no Google account, and not tied to a sign-in flow. Docs

final res = await smartAuth.requestPhoneNumberHint();
if (res.hasData) {
  // Use the phone number
} else {
  // Handle the error
}

SMS with User Consent

The user confirms access to a single SMS in a system dialog. No app signature needed. API overview

final res = await smartAuth.getSmsWithUserConsentApi();
if (res.hasData) {
  // The code is null when the SMS arrived but no code could be extracted
  final code = res.requireData.code;
  if (code == null) return;
  // Use the code
} else if (res.isCanceled) {
  // The user dismissed the dialog
} else {
  // Handle the error
}

Verification flow

1. The user starts SMS verification, typing a phone number or picking one with requestPhoneNumberHint.
2. Your app asks your server to verify the number (user ID, phone number, or both).
3. At the same time, the app calls getSmsWithUserConsentApi to show the consent dialog.
4. Your server sends an SMS with a one-time code.
5. When the SMS arrives, the plugin extracts the code from it. Send it back to your server.
6. Your server verifies the code and records the account as verified.

SMS Retriever

Fully automatic, with no user interaction and no extra permissions. The SMS must contain your app's hash. API overview

final res = await smartAuth.getSmsWithRetrieverApi();
if (res.hasData) {
  // The code is null when the SMS arrived but no code could be extracted
  final code = res.requireData.code;
  if (code == null) return;
  // Use the code
} else {
  // Handle the error
}

Verification flow

1. The user starts SMS verification, typing a phone number or picking one with requestPhoneNumberHint.
2. Your app asks your server to verify the number (user ID, phone number, or both).
3. At the same time, the app calls getSmsWithRetrieverApi to start listening for the SMS.
4. Your server sends an SMS with a one-time code and a hash that identifies your app.
5. Google Play services uses the hash to route the message to your app.
6. The plugin extracts the code from the message. Send it back to your server.
7. Your server verifies the code and records the account as verified.

Get your app's hash with getAppSignature and have your backend end every SMS with it (the message must be short, contain the code and end with the 11-character hash). The hash differs between debug and release builds.

final res = await smartAuth.getAppSignature();
if (res.hasData) {
  print(res.data); // e.g. kg+TZ3A5qzS
}

Your ExampleApp code is: 123456
kg+TZ3A5qzS

Remove listeners

The plugin removes listeners after it receives a code. To stop earlier, for example in dispose:

smartAuth.removeUserConsentApiListener();
// or
smartAuth.removeSmsRetrieverApiListener();

Credential Manager

Get, save and clear passwords and passkeys. isCanceled is true when the user dismisses the dialog. Docs

// Show saved passwords and passkeys
final result = await smartAuth.getCredential(
  passwordOption: SmartAuthPasswordOption(),
  publicKeyOptions: [SmartAuthPublicKeyOption(requestJson: requestJsonFromServer)],
);
final credential = result.data;
// credential.type is password or publicKey
// password:  credential.id, credential.password
// passkey:   credential.authenticationResponseJson

// Save a password
await smartAuth.createPasswordCredential(id: 'user@example.com', password: 'secret');

// Create a passkey, send registrationResponseJson to your server
final created = await smartAuth.createPublicKeyCredential(requestJson: requestJsonFromServer);

// Android 14+: fetch the data first to show the account selector faster
final prepared = await smartAuth.prepareGetCredential(passwordOption: SmartAuthPasswordOption());
if (prepared.hasData) {
  final credential = await smartAuth.getPreparedCredential();
}

// On sign out
await smartAuth.clearCredentialState();

• prepareGetCredential and getPreparedCredential need Android 14 or higher. Below that they fail with UNSUPPORTED.
• Only privileged apps can see which credentials prepareGetCredential found. The has* fields of SmartAuthPreparedCredential are null for other apps. It still makes the next getPreparedCredential faster.

Error codes

Failed results contain one of these codes in error:

Code	Meaning
NO_CREDENTIAL	Nothing to show, the user has no matching saved credentials
INVALID_REQUEST	The request is incomplete, e.g. getCredential without any option
NO_ACTIVITY	There is no foreground activity to show the dialog on
UNSUPPORTED	The method needs a newer Android version
NO_PREPARED_CREDENTIAL	getPreparedCredential was called before prepareGetCredential
GET_CREDENTIAL_FAILED, CREATE_CREDENTIAL_FAILED, PREPARE_GET_CREDENTIAL_FAILED, CLEAR_CREDENTIAL_STATE_FAILED	The Credential Manager reported an error

Requirements

Flutter 3.44 or above. The plugin is tested with Flutter 3.47.

Capability	Google Play services	Android version
SMS Retriever, SMS User Consent, Phone Number Hint	Required	7.0+ (API 24)
Credential Manager	Required on Android 13 and below	7.0+ (API 24)
prepareGetCredential, getPreparedCredential	–	14+ (API 34)

Added by this package

Requirement	Minimum
compileSdk	35 or above (it doesn't drop any devices)
JDK that runs Gradle	17 or above (JDK 25 doesn't work with Gradle 8.14)
Java source and target	11 or above

// android/app/build.gradle
android {
    compileSdk = 35

    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_11
        targetCompatibility = JavaVersion.VERSION_11
    }
}

Android build tools

AGP, Gradle and Kotlin versions are dictated by your Flutter version. Flutter checks them when building and tells you what to upgrade, and a project created with flutter create already has them. For example Flutter 3.47 requires:

Tool	Minimum
Android Gradle Plugin (AGP)	8.11.1 (Flutter will move to 9.0.1)
Gradle	8.14 (Flutter will move to 9.1.0)
Kotlin	2.2.20 (Flutter will move to 2.3.20)

The plugin also works with AGP 9, where Kotlin is built in, see the migration guide. With AGP 9 you don't need the kotlin-gradle-plugin classpath or the org.jetbrains.kotlin.android plugin, and kotlinOptions is deprecated.

Migrating

To 4.x: the Dart API is unchanged. The new requirements are Flutter 3.44 / Dart 3.12, compileSdk 35 or above, and the AGP, Gradle and Kotlin versions your Flutter version requires (see Requirements). The plugin's own minSdkVersion is 21.

From 2.x to 3.x:

2.x	3.x
SmartAuth()	SmartAuth.instance
getSmsCode() returning SmsCodeResult	getSmsWithRetrieverApi() / getSmsWithUserConsentApi() returning SmartAuthResult<SmartAuthSms>
res.succeed && res.codeFound, res.code	res.hasData, res.data?.code
getAppSignature() returning String?	returns SmartAuthResult<String>, read the value with res.data
removeSmsListener()	removeSmsRetrieverApiListener() / removeUserConsentApiListener()

Contributing

PRs are welcome. Read the contributing guide first, and see the example app for full usage.

---