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Easy on Humans, Hard on Bots: Making reCAPTCHA Work for You

Learn about how reCAPTCHA can protect your website from fraud and discover the pros, cons, and best practices for this valuable security tool.

What is reCAPTCHA?

CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. A CAPTCHA protects websites from spam and bots by asking internet users to complete a test designed to be easy for a real person but hard for an automated bot account. CAPTCHAs provide verification and security to websites, apps, and other electronic services.

Google's reCAPTCHA does more than just prove that you're an actual human. It can also thwart malicious tactics—for example, credential stuffing, a practice in which hackers use lists of compromised account names and passwords to try to break into user accounts on other sites.

The history of reCAPTCHA

reCAPTCHA was designed in 2007 as a tool for digitizing books. People were shown text that computers could not recognize and asked to type in what they saw. In 2009, Google acquired reCAPTCHA and began using it to improve internet security. Today, it's widely used for verification to protect against spam and bots and is an important tool for maintaining security and integrity of online systems.

reCAPTCHA, v2, v3—what's the difference?

reCAPTCHA uses image recognition, audio recognition, behavioral analysis, and machine learning to determine whether the user is human or not. It's the most popular service—installed on millions of sites, with more than 97% of market share.

Currently, there are two versions of reCAPTCHA:

  • reCAPTCHA v2 requires users to solve a challenge or click a checkbox. It allows website owners to customize the appearance and behavior of the challenge.
  • reCAPTCHA v3 works in the background and does not require any interaction. It generates a score based on factors like user behavior, the time of day, and other contextual information.

How reCAPTCHA works

A site using reCAPTCHA includes a small piece of code (a "script") that handles the challenge-and-response process. As someone interacts with the challenge, reCAPTCHA collects data on their behavior such as their keystrokes, mouse movement and timing, and browsing history.

The script communicates with Google's server using a secret key to encrypt the communication. The secret key is unique to each website and is generated when the website owner sets up reCAPTCHA.

Google's algorithms compare the data with known human and bot behavior and may ask the user to complete additional challenges or block their access.

Artificial intelligence (AI) and pattern recognition

reCAPTCHA technology makes use of AI to perform an advanced risk analysis with every new site user, evaluating things like IP address, browser and device information, and past browsing behavior. Then reCAPTCHA assigns a risk score. A low risk score indicates a high likelihood that the user is human, while a high risk score suggests that it may be a bot. If the program suspects a bot or needs more information, it asks the user to do a reCAPTCHA test.

Types of reCAPTCHA tests

CAPTCHA tests come in many forms and have been adapted to become more sophisticated, harder to fool, and less intrusive. The reCAPTCHA type depends on various factors, including the security settings of the site, the context, and the type of activity.


The website visitor is shown a series of letters and numbers that have been distorted or partially obscured and is asked to type them in the correct sequence.

Image recognition

The user sees distorted, cropped, or partially obscured images and must select those matching a specific description; for example, images containing street signs or vehicles.


Sometimes called "no CAPTCHA reCAPTCHA," this method just requires people to check a box to confirm that they are not a robot. Google uses background information, such as the user's IP address and browser data, to verify that they are human users.

User behavior assessment

Often there's no checkbox or CAPTCHA challenge at all. In this "invisible" version, the system does the verification process automatically and the checkbox only appears if Google suspects that it might be dealing with a bot. This makes the user experience smoother and less intrusive.

reCAPTCHA pros and cons

It's helpful to examine the pros and cons of reCAPTCHA to determine if it's right for you.


Increased privacy

While reCAPTCHA is primarily designed to improve security, it can also help enhance privacy by preventing unauthorized access to sensitive information like your customers' contact info.

Limits fake users

It's no secret how much fraud there is on the internet. Using the reCAPTCHA service helps ensure that those who can solve the reCAPTCHA challenge are likely to be the visitors you want.

Automatically screens user comments

Offering customers the ability to leave user reviews or comments on social media posts can be a great way to build customer engagement. But manually screening for abusive comments and spammers is labor intensive.

Free service for small businesses

Google's reCAPTCHA is a free service for anyone with up to one million security checks per month. Beyond that, Google has launched reCAPTCHA Enterprise to help larger-scale customers prevent spam and abuse.


Extra user interaction

You want to make your visitors' experience as easy and smooth as possible, but having to solve a challenge for verification puts an extra step or two in their way.

Accessibility challenges

Those who are visually impaired may find CAPTCHAs challenging. The latest versions include an audio option that allows someone to listen to an audio clip and respond verbally.

Good users can be marked as suspicious

No system is perfect. When people are incorrectly identified as bots, for example, they may have to go through additional steps to move forward or find their access blocked entirely.

Favors Google users

While reCAPTCHA is owned and operated by Google, it can be used by any website or application. However, it works by determining whether you have Google cookies on your browser. So anyone signed into a Google account may find reCAPTCHA smoother and more frictionless than non-Google users.

Bots are getting better

Inevitably, malicious actors are always improving their ability to get around verification services. Although reCAPTCHA works to stay ahead of them, no system is perfect and creative hackers will sometimes find a way to break through.

Alternatives for reCAPTCHA users

Although Google's program has the majority of the market share, it's not the only program that uses CAPTCHA verification to protect websites against fraud. Some other options are:

  • Akismet: If your site is designed in WordPress, this plugin uses machine learning algorithms to identify and block spam comments on your website.
  • BotDetect: A versatile CAPTCHA technology, this program allows users to customize the challenge and form design in a way that makes the most sense for their customers.
  • KeyCAPTCHA: This CAPTCHA technology uses interactive puzzles to verify identity instead of traditional letter and number recognition.
  • hCaptcha: This is a program developed to be more accessible for people with disabilities. It includes a range of challenges— for example, image recognition, audio recognition, and interactive puzzles. It also supports multiple languages.

Tips for website owners

If reCAPTCHA seems like the right choice for you, read on for some tips about how to put it to use. Google provides a reCAPTCHA support page if you have any questions or run into trouble.

When to use reCAPTCHA

reCAPTCHA can protect your site from spam and abuse and reassure legitimate customers that their data is safe. Here are some of the times when you may find reCAPTCHA useful:

  • Registration: If you allow people to create an account on your website, reCAPTCHA can help prevent automated users from abusing and spamming your system. Learn how to use reCAPTCHA for signup forms on your Mailchimp site.
  • Contact forms: Preventing spam gives you more time to respond to legitimate messages.
  • Login pages: Prevent hackers from attempting to guess user passwords or conducting other types of attacks.
  • E-commerce transactions: CAPTCHAs can help stop fraudulent transactions or scraping of your product data.

How to install reCAPTCHA

Here are the steps to install reCAPTCHA on your site:

  1. Sign up for an application programming interface (API) key by visiting the Google reCAPTCHA website, creating a new account, and specifying the internet domains where you will be using the service.
  2. Choose the version of reCAPTCHA (v2 or v3) that best fits your needs.
  3. Integrate the reCAPTCHA code into your site or application. This typically involves adding JavaScript code to your web pages and modifying any relevant form submission scripts to include reCAPTCHA validation.
  4. Use the reCAPTCHA test site to test your integration and make sure that your forms are properly validated.

You can find detailed documentation and tutorials on the Google reCAPTCHA website to help you with the integration process.

How to update reCAPTCHA

Keeping your security program updated is important. You can:

  • Check your version of reCAPTCHA by looking at your site's source code. It may be time to update if you are using an older version.
  • Replace the old code with updated code, which you can find on the reCAPTCHA website along with instructions for implementation.

The future of CAPTCHAs

Like any computer program designed to protect against abuse, reCAPTCHA always needs to stay one step ahead of malicious actors and advanced bots. Here are some ways you may see CAPTCHA technology used in the future:

  • Expansion to other devices and platforms: With security an increasing concern, CAPTCHA challenges may become more common on wearable or smart home devices.
  • More invisibility: The checkbox may be a thing of the past. Future CAPTCHAs are likely to operate in the background, without requiring visitors to submit answers to a security challenge.
  • Accessibility improvements: In addition to an audio version, future CAPTCHA services may include alternative input methods, more support for screen readers, or other technologies.

If reCAPTCHA seems like the right solution for you, sign up for Google's free reCAPTCHA service for your small business or check out another CAPTCHA provider to protect your website from hackers, bots, and automated accounts!

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