An Internet bot (also called a web robot or robot), or simply bot, is a software application that runs automated tasks (scripts) on the Internet, usually with the intent to imitate human activity, such as messaging, on a large scale. An Internet bot plays the client role in a client–server model whereas the server role is usually played by web servers. Internet bots are able to perform simple and repetitive tasks much faster than a person could ever do. The most extensive use of bots is for web crawling, in which an automated script fetches, analyzes and files information from web servers. More than half of all web traffic is generated by bots.
Efforts by web servers to restrict bots vary. Some servers have a robots.txt file that contains the rules requesting how bots should behave on website. Any bot that does not follow the rules could, in theory, be denied access to or be removed from the affected website. A website owner cannot force a bot to follow the rules or ensure that a bot's creator or implementer reads or acknowledges the robots.txt file. Some bots are "good", e.g. search engine spiders, while others are used to launch malicious attacks on political campaigns, for example.