Abstract: There is provided a method and system for effective detection of web application version which uses such a data set that allows with minimal number of queries to web server to detect version of web application installed on it. The method is based on calculation of check sum of files and sorting them so that the most frequently changing from version to version files are checked first. In parallel, a lot of potentially suitable versions are stored and with each request to the server the set is shortened until no elements remain. Web server answers which do not match any of pre-calculated hash sums are stored for further processing in order to complement existing database of versions.