Any website finds identification of visitors crucial. Usually, cookie files are used, but they have several drawbacks, as users can delete or block them (e.g. by activating the “incognito” mode in web browsers). Besides, cookies fail to identify a user who uses several different web browsers, even if he or she connects using the same device. Hence the idea of a browser fingerprint — a unique user identifier which does not change between successive sessions and which does not depend on selected web browser.