What Are The Different Types of CAPTCHAs

One of the earliest CAPTCHA types, text-based CAPTCHAs are usually a combination of random Anti-captcha letters and characters presented in an alienated format. Characters are turned, scaled, distorted, incensed – all for the purpose of making it difficult for the bots to recognize them. In some cases, letters and/or numbers are overlapped with various elements, such as colors, dots, lines, arrows, background noise, etc.

Due to a more complex nature, this type of CAPTCHAs is a preferred anti-bot solution over text-based ones. An image-based CAPTCHA’s working principle is pretty simple – it displays several pictures in a grid and asks the user to select a specific type of image. For instance, if the theme is “traffic lights,” you have to click on every image that contains a traffic light. While image CAPTCHAs are usually easier for human users to interpret, they are a bigger struggle for most bots as these tests require both image recognition and semantic classification.