Application security is one of the key aspects necessary for its proper functioning. Ensuring security consists primarily in conducting regular penetration tests and checking the vulnerability of the application to various types of attacks. The recommended solution is to use tools dedicated to detecting security holes in applications. Choosing the right tool from among those available on the market can be difficult. This article presents a comparative analysis of the effectiveness of popular application security testing tools in terms of the number of detected vulnerabilities. The analysis was based on the obtained results of scanning two Internet applications containing a number of security vulnerabilities, used to learn ethical hacking.