Did you know that bad bots cause billions of dollars in financial losses yearly? Bot fraud is an undeniable threat to the worldwide web. Fraudsters have been exploiting systems with automated attacks since the early days of the internet, and CAPTCHA has been the key solution to stopping relentless bot attacks by telling bots and humans apart.

The fight has never been one-sided. However, backed by massive financial motivation and advancing computer technologies, fraudsters found ways to bypass or crack CAPTCHA measures, leaving the ecosystem vulnerable to bot attacks. In turn, defenders had to get creative with their CAPTCHAs to stop the alarming bot threat.

Factors to consider when choosing a CAPTCHA

Over two decades of confrontation and billions of dollars lost by underprepared victims, CAPTCHA has evolved into various forms to protect the internet from bad bot threats. When deciding which type of CAPTCHA to use on your website or mobile app, it is important to take a number of factors into consideration.

Here's a breakdown of the factors to consider when choosing a CAPTCHA:

  1. Security: The main purpose of a CAPTCHA is to prevent automated attacks generated by bots and ensure that only humans can access your website or app. Therefore, the level of security that a CAPTCHA provides should be the top consideration.
  2. User experience: CAPTCHAs can often be frustrating and time-consuming for users, which can lead to increased bounce rates and decreased engagement. Therefore, it's important to consider how the CAPTCHA will affect the overall user experience on your website or app.
  3. Ease of implementation: Implementing a CAPTCHA can be a technical and time-consuming process. It's important to choose a CAPTCHA that is easy to implement and won't require significant development resources.
  4. Accessibility: Many CAPTCHAs may pose challenges for users with disabilities, such as visual or hearing impairments. It's important to choose a CAPTCHA that is accessible to all users.
  • By taking these factors into account, you can select a CAPTCHA that not only protects your website or app from automated attacks but also provides a positive user experience for all users.

Four Generations Explained

To understand how to weigh up the factors and threats you may face, we must look at the past. CAPTCHA has evolved in 4 waves since the early 2000s. Each of them has both pros and cons. Here's a closer look at the advantages and drawbacks of 4 generations.

First-Generation CAPTCHA

The first-generation CAPTCHA is the oldest and simplest type of CAPTCHA. It uses distorted letters and numbers that are relatively easy for humans to decipher but can be easily cracked by today's bots with the advancements of AI technology and OCR systems. Bots got better at recognizing these noisy characters than humans. While this type of CAPTCHA is easy to implement and can be effective against some basic attacks, it is not suitable for websites or mobile apps that require a higher level of security.

First Generation Standard CAPTCHAs


  • Easy to implement
  • Suitable for websites with low-security needs


  • Vulnerable to advanced bots
  • Can be frustrating for users to recognize


Text-based CAPTCHAs Are Trivial For Bot Mitigation

No matter how distorted a Standard CAPTCHA is, it’s easy for sophisticated bots and hard for all humans

Second-Generation CAPTCHA

The second generation of CAPTCHA had left the text-based input approach for more innovative challenges that were deemed it's very difficult for bots to bypass at the time. It uses images, visual comparisons, and even math challenges, to make it harder for bots to bypass. This type of CAPTCHA is more effective than the first generation, but can still be solved by advanced bots.


  • Harder to bypass than the first generation
  • Can be customized to match website or app UI


  • Some users may have difficulty with certain challenges, like math ones
  • Still vulnerable to advanced bots

If a human can pass a challenge, a machine learning algorithm can be trained to pass it too

Third-Generation CAPTCHA

The third-generation CAPTCHA uses puzzles and games to verify that the user is human. It is designed to be easy for humans to solve, but difficult for bots to complete. This type of CAPTCHA can include puzzles such as Sudoku or games like Tic Tac Toe or memory challenges. While third-generation CAPTCHAs are more effective than the first and second-generation, they can be time-consuming for users.


  • Difficult for bots to bypass
  • Can be entertaining for some users


  • Can be time-consuming for users
  • Some users may find puzzles or games difficult to solve

Fourth Generation CAPTCHA

The fourth generation CAPTCHA uses advanced artificial intelligence and machine learning algorithms to identify and verify human behavior, such as mouse movements and keystrokes. This type of CAPTCHA is designed to be very difficult for bots to solve. Fourth-generation CAPTCHAs are currently the most advanced type of CAPTCHA available.


  • Very difficult for bots
  • Easy and seamless for users


  • Involves code experience in the implementation
  • Requires advanced artificial intelligence and machine learning technology

 The fourth-generation CAPTCHA is based on the comprehensive decision-making between the inherent biological characteristics of humans and the environmental information of the operation.

GeeTest CAPTCHA risk control engine analyzes the biometric and environmental data to determine whether the user is human or a bot

How to achieve the best practice with CAPTCHA?

Here are some tips and best practices for implementing CAPTCHA effectively:

  1. Choose the right CAPTCHA generation: As previously discussed, there are different generations of CAPTCHAs, each with its own advantages and limitations. It's important to choose the right type of CAPTCHA for your website or app based on the security level you require, the user experience you want to provide, and the accessibility needs of your users.
  2. Place the CAPTCHA in the right session: It's important to place the CAPTCHA on a page or sessions where you want to filter your users and protect your website assets, and remember to ensure it's easily visible and accessible to users. Generally, it's recommended to place the CAPTCHA at the end of a form or registration process to prevent bots from submitting automated form entries.
  3. Customize the CAPTCHA: Customizing the CAPTCHA can help improve the user experience and make it more engaging for users. For example, you can customize the background or colors of the CAPTCHA to match your brand or use a custom message or image to make it more visually appealing.
  4. Use CAPTCHA sparingly: Overusing CAPTCHAs can negatively impact the user experience and discourage users from using your website or app. It's important to use CAPTCHA only when necessary, such as during registration or when submitting a form, and avoid using it excessively.
  5. Monitor CAPTCHA effectiveness: Keep track of the effectiveness of your CAPTCHA by monitoring the number of failed attempts and verifying that only human users are able to access your site or app. This can help identify potential issues or weaknesses in your CAPTCHA implementation.

Implementing CAPTCHA effectively involves choosing the right type of CAPTCHA. Choosing the most suitable one depends on factors such as security, user experience, ease of implementation, and accessibility needs. For websites or applications that require high-security levels, fourth-generation CAPTCHAs may be the best option due to their advanced technology. For websites or applications that prioritize user experience, third-generation CAPTCHAs may be a better choice since they use more engaging images and audio.

Stop bots with GeeTest CAPTCHA

GeeTest CAPTCHA v4 is a highly recommended option for websites or applications that require advanced security measures. As a fourth-generation CAPTCHA, it uses advanced AI and machine learning algorithms to identify and verify human behavior, making it hard for bots to bypass. Additionally, its customization options in terms of UI and UX make it easy to integrate into the design of your website or application seamlessly.

GeeTest CAPTCHA v4 also offers adaptive security strategies, meaning that it can adjust its security measures based on the level of risk it detects. This ensures that your website or application is always protected from potential threats.

Moreover, GeeTest CAPTCHA v4's dashboard allows customers to track the effectiveness of CAPTCHA on their websites or apps, which can help identify potential issues or weaknesses in implementation. This feature ensures that you can monitor the security level of your website or application in real time.

GeeTest CAPTCHA v4 is a reliable and customizable option for websites or applications that require high-security levels, while also providing excellent user experience and accessibility.

By following these tips and best practices we discussed in this article, you can help ensure that your website or app remains secure while providing a positive user experience.

Start your free trial
Over 320,000 websites and mobile apps worldwide are protected by GeeTest captcha

Hayley Hong

Content Marketing @ GeeTest