What is a User Agent?
A user agent is a type of software that retrieves and renders web content so that users can interact with it. The most common examples are web browsers and email readers.
More About User Agents
A user agent acts between a web server and an online user. This contains a characteristic string in its HTTP request header that identifies the user agent to a server. Using this information, servers can determine the operating system, application type, or software version of the user agent. Common examples of user agents are browsers like Mozilla Firefox, Google Chrome, and Safari.
Other applications can also be user agents, including crawlers, game consoles, screen readers, link checkers, and legacy operating systems. By editing a robots.txt file, you can instruct a search engine user agent, such as Googlebot, to crawl or not crawl certain pages on your website.