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What is a reCAPTCHA


ReCAPTCHA is a technology used to protect websites and applications from automated submissions by computer bots (spam bots). ReCAPTCHA was developed by the Google subsidiary "Duolingo" and uses visual and acoustic tests to distinguish humans from bots.

What is a reCAPTCHA?

The Google reCAPTCHA is a free service that uses distorted images, words and shapes to identify whether a web user is a human or a computer. You have probably seen this yourself the distorted text at the bottom of web registration forms.

The concept of "Captcha" has a very interesting history. A university in Pennsylvania (the Carnegie Mellon University) developed the CAPTCHA to prevent bots from making fraudulent transactions. Therefore, deciphering these distorted letters and words can only be completed by a human.

Furthermore, the loosening of the ReCAPTCHA's to digitize books and letters. When a book is scanned, the software tries to decode the words and copy them digitally. Occasionally, however, the software cannot recognize the letters, especially in the case of extremely old books, which are particularly difficult to read. Therefore presents reCAPTCHA you two images, which need to be solved. The first is a standard captcha that ensures that you are not a bot. The second CAPTCHA to be solved is then an original scanned image from a book. The input of your answer can thus be captured and evaluated by the digitization software.

Why are the images sometimes random?

Most of the time the images make sense to a human, but occasionally mathematical symbols, Greek equations, or even randomly generated hard-to-perceive images appear. This is because the software cannot recognize and decode the image. By solving the ReCAPTCHA's, these symbols can then also be digitally recognized by the software.

How does Google's reCAPTCHA work? - Purpose and operation

The one offered by Google reCAPTCHA-service is the most widely used captcha service and has been adopted by many popular websites. These try to prevent automated bots from performing potentially harmful activities. Google announced that the deployment of a new reCaptcha-mechanism, should be more people-friendly and safer.

When visiting one of reCAPTCHA protected website, the request is analyzed by an advanced risk analysis system, which decides what type of captcha challenge will be presented to the user. Then the user has 55 seconds to answer it. If he fails to do it in this time, the popup is closed and the user has to click the checkbox again to get a new captcha.

Based on the security level assigned to the specific request, Google's advanced risk analysis system selects what kind of challenge the user will get. The different versions have a different difficulty level, which is applied depending on the situation. If a user completes several challenges incorrectly in a short period of time, the system provides increasingly difficult captchas.


The biggest advantage of ReCAPTCHA is that it provides an effective and simple way to protect websites and applications from automated input by bots. ReCAPTCHA is easy to implement, as it is a free tool and it is completely free. Moreover, it requires ReCAPTCHA very little development work, since it has a simple API that can be easily integrated into a website or application.


A disadvantage of ReCAPTCHA is that it can sometimes be difficult to pass the tests, especially for users who have poor eyesight or hearing problems. In addition, asking a user to pass the tests multiple times can also result in a negative user experience.

Use cases

Google reCAPTCHA is a security service used to distinguish human users from automated bots. In the context of SEO and web development reCAPTCHA can be useful in various use cases to improve the user experience while increasing the security of the website. Here are some use cases where reCAPTCHA can be useful:

Contact forms

One of the most common applications for reCAPTCHA is the contact form. Through the implementation of reCAPTCHA the risk of spam messages is minimized, which increases not only the user experience but also the credibility of the website.

Comment sections

If your website offers a commenting function, you can reCAPTCHA help prevent automated spam comments. This is especially important for blogs and news sites, where the quality of discussion is an important aspect of the user experience.

Login and registration pages

reCAPTCHA can increase the security of user login and registration by preventing brute force attacks. This increases user trust in your website and improves the overall security level.

E-commerce and checkout processes

In E-commerce-platforms can reCAPTCHA be integrated during the checkout process to minimize fraud attempts and increase transaction security.

User Generated Content (UGC)

If your website allows users to upload their own content (e.g., photos, articles, reviews), you can reCAPTCHA help prevent the upload of spam or harmful content.

Search functions

Some websites implement reCAPTCHA also in their search function to prevent automated queries that could load the servers.

Online surveys and polls

For online surveys or polls, you can reCAPTCHA ensure that results are not skewed by automated bots.

It is important to note that the use of reCAPTCHA can easily negatively impact the user experience, as it represents an additional step in the interaction process. Therefore, it should be implemented carefully and only in scenarios where the advantages in terms of security and spam avoidance outweigh the possible disadvantages in terms of user experience.


ReCAPTCHA provides a simple and effective way to protect websites and applications from automated input by bots. It is a low-cost and easy-to-implement technology, and is particularly suitable for websites and applications that require high security.

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What is reCAPTCHA? arrow icon in accordion
ReCAPTCHA is a service that helps website visitors make sure they are real humans and not a script or bot. It uses an optical scanning system to ensure that only human users interact.
How does ReCAPTCHA work? arrow icon in accordion
ReCAPTCHA uses an optical scanning system to make users fill out a small captcha form. This captcha form contains an image with a series of letters and numbers that the user must enter to confirm that they are not a bot. If the input is correct, the request is sent to the ReCAPTCHA server and the user is confirmed as genuine.
Why should websites use ReCAPTCHA? arrow icon in accordion
ReCAPTCHA provides websites with a secure and efficient way to ensure that users are genuine. ReCAPTCHA protects websites from spam, fraud and abuse. It is a simple and effective way to keep control over users and their actions.
What is the Google reCAPTCHA? arrow icon in accordion
Google reCAPTCHA is a service from Google that helps websites identify and validate users. It uses a combination of optical sensing and machine learning to determine whether a user is human or bot.
Is ReCAPTCHA free of charge? arrow icon in accordion
Yes, ReCAPTCHA is a free service. It is provided by Google and there is no need to pay any fees to use it.
Why should I use ReCAPTCHA? arrow icon in accordion
There are many reasons why you should use ReCAPTCHA on your website. For one, it protects your website from spam, fraud and abuse by ensuring that users are genuine. It also provides an effective way to monitor and control your user activity.
How do I update my ReCAPTCHA? arrow icon in accordion
ReCAPTCHA is automatically updated when new versions are released. However, it is possible to update the ReCAPTCHA system manually by clicking the "Update" button on the ReCAPTCHA website.
Can I customize my ReCAPTCHA form? arrow icon in accordion
Yes, you can customize the look of your ReCAPTCHA form using different theme elements such as color, font and background images. To save the changes after updating the settings, you need to click the "Update" button on the ReCAPTCHA website.
Can I use ReCAPTCHA on my website? arrow icon in accordion
Yes, you can use ReCAPTCHA on your website. All you need to do is to paste the HTML code fragment on your website. Once you do that, ReCAPTCHA will automatically appear on your website.
Which browsers support ReCAPTCHA? arrow icon in accordion
ReCAPTCHA is supported by all popular web browsers like Chrome, Firefox, Edge and Safari. It is also compatible with all popular mobile browsers.

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