Developer's Guide

Google offers reCAPTCHA (v3 and v2) and reCAPTCHA Enterprise to help you protect your sites from fraudulent activities, spam, and abuse. To know more about the features of reCAPTCHA and reCAPTCHA Enterprise, see Comparison of features between reCAPTCHA versions.

This document provides an overview of Google reCAPTCHA v3 and v2. For information about reCAPTCHA Enterprise, see the reCAPTCHA Enterprise documentation.

Audience

This documentation is designed for people familiar with HTML forms, server-side processing or mobile application development. To install reCAPTCHA, you might need to edit some code.

We hope you find this documentation easy to follow. You can ask a question about reCAPTCHA on Stack Overflow, using the tag recaptcha.

Overview

To start using reCAPTCHA, you need to sign up for an API key pair for your site. The key pair consists of a site key and secret key. The site key is used to invoke reCAPTCHA service on your site or mobile application. The secret key authorizes communication between your application backend and the reCAPTCHA server to verify the user's response. The secret key needs to be kept safe for security purposes.

First, choose the type of reCAPTCHA and then fill in authorized domains or package names. After you have accepted the terms of service, click Register to get new API key pair.

Now, perform the following steps to add reCAPTCHA to your site or mobile application:

  1. Choose the client-side integration:
  2. Verify the user's response.

Comparison of features between reCAPTCHA v3 and reCAPTCHA v2

The following table shows a comparison of the features in reCAPTCHA v3 and reCAPTCHA v2.

Feature reCAPTCHA v3 reCAPTCHA v2
Cost

For more information, see Pricing.

Free up to 1 million assessments per month* Free up to 1 million assessments per month*
"I'm not a robot" widget support No Yes
Score granularity (security-review required) 4 levels None