SafetyNet reCAPTCHA API

The SafetyNet service includes a reCAPTCHA API that you can use to protect your app from malicious traffic.

reCAPTCHA is a free service that uses an advanced risk analysis engine to protect your app from spam and other abusive actions. If the service suspects that the user interacting with your app might be a bot instead of a human, it serves a CAPTCHA that a human must solve before your app can continue executing.

This document explains how to integrate the reCAPTCHA API from SafetyNet into your app.

Additional terms of service

By accessing or using the reCAPTCHA API, you agree to the Google APIs Terms of Service and to the following reCAPTCHA Terms of Service. Please read and understand all applicable terms and policies before accessing the APIs.

Register a reCAPTCHA key pair

To register a key pair for use with the SafetyNet reCAPTCHA API, navigate to the reCAPTCHA Android signup site, then complete the following sequence of steps:

1. In the form that appears, provide the following information:

   • Label: A unique label for your key. Typically, you use the name of your company or organization.
   • reCAPTCHA type: Select reCAPTCHA v2, then reCAPTCHA Android.
   • Packages: Provide the package name of each app that uses this API key. In order for an app to use the API, the package name that you enter must exactly match the app's package name. Enter each package name on its own line.
   • Owners: Add an email address for each individual in your organization who monitors your app’s reCAPTCHA assessments.

2. Select the Accept the reCAPTCHA Terms of Service checkbox.

3. Send alerts to owners: Select this checkbox if you want to receive emails about the reCAPTCHA API, then click Submit.

4. On the page that appears next, your public and private keys appear under Site key and Secret key, respectively. You use the site key when you send the verify request, and you use the secret key when you validate the user response token.

Add the SafetyNet API dependency

Before using the reCAPTCHA API, add the SafetyNet API to your project. If you are using Android Studio, add this dependency to your app-level Gradle file. For more information, see SafetyNet API setup.

Use the reCAPTCHA API

This section describes how to call the reCAPTCHA API to send a CAPTCHA verification request and receive the user response token.

Send the verify request

To invoke the SafetyNet reCAPTCHA API, you call the verifyWithRecaptcha() method. Usually, this method corresponds to the user's selecting a UI element, such as a button, in your activity.

When using the verifyWithRecaptcha() method in your app, you must do the following:

• Pass in your API site key as a parameter.
• Override the onSuccess() and onFailure() methods to handle both possible outcomes of the verification request task. In particular, if the API passes an instance of ApiException into onFailure(), you need to handle each possible status code that you can retrieve using getStatusCode().

The following code snippet shows how to invoke this method:

fun onClick(view: View) {
    SafetyNet.getClient(this).verifyWithRecaptcha(YOUR_API_SITE_KEY)
            .addOnSuccessListener(this as Executor, OnSuccessListener { response ->
                // Indicates communication with reCAPTCHA service was
                // successful.
                val userResponseToken = response.tokenResult
                if (response.tokenResult?.isNotEmpty() == true) {
                    // Validate the user response token using the
                    // reCAPTCHA siteverify API.
                }
            })
            .addOnFailureListener(this as Executor, OnFailureListener { e ->
                if (e is ApiException) {
                    // An error occurred when communicating with the
                    // reCAPTCHA service. Refer to the status code to
                    // handle the error appropriately.
                    Log.d(TAG, "Error: ${CommonStatusCodes.getStatusCodeString(e.statusCode)}")
                } else {
                    // A different, unknown type of error occurred.
                    Log.d(TAG, "Error: ${e.message}")
                }
            })
}

public void onClick(View v) {
    SafetyNet.getClient(this).verifyWithRecaptcha(YOUR_API_SITE_KEY)
        .addOnSuccessListener((Executor) this,
            new OnSuccessListener<SafetyNetApi.RecaptchaTokenResponse>() {
                @Override
                public void onSuccess(SafetyNetApi.RecaptchaTokenResponse response) {
                    // Indicates communication with reCAPTCHA service was
                    // successful.
                    String userResponseToken = response.getTokenResult();
                    if (!userResponseToken.isEmpty()) {
                        // Validate the user response token using the
                        // reCAPTCHA siteverify API.
                    }
                }
        })
        .addOnFailureListener((Executor) this, new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    if (e instanceof ApiException) {
                        // An error occurred when communicating with the
                        // reCAPTCHA service. Refer to the status code to
                        // handle the error appropriately.
                        ApiException apiException = (ApiException) e;
                        int statusCode = apiException.getStatusCode();
                        Log.d(TAG, "Error: " + CommonStatusCodes
                                .getStatusCodeString(statusCode));
                    } else {
                        // A different, unknown type of error occurred.
                        Log.d(TAG, "Error: " + e.getMessage());
                    }
                }
        });
}

Validate the user response token

When the reCAPTCHA API executes the onSuccess() method, the user has successfully completed the CAPTCHA challenge. However, this method only indicates that the user has solved the CAPTCHA correctly. You still need to validate the user's response token from your backend server.

To learn how to validate the user's response token, see Verifying the user's response.