What Is My User Agent?

User Agent is a client-side application that browsers and other Internet services use to show websites information about themselves in a specific line.

User Agent usually looks like a separate file with several lines of code intended specifically for identification. It also contains information about the device used, the clients OS, etc. User Agent solved the problem when certain countries could use ONLY those browsers that were developed specifically for them.

Where User Agent is used

• Cross-browser compatibility. We all know that different browsers can open the same page. Thanks to user agents, you can understand which browser the client has opened and provide the version of the site that will be displayed adequately in it, without the wrong layout, fonts, etc.
• Adaptive design. Web servers take information about the device type (for example, mobile or desktop) from the user agent file and issue the version of the site that was made specifically for it.
• Authentication. User agents are also used to identify unhealthily repetitive requests and prohibit possible actions by intruders.
• Analytics and statistics. User agent is an opportunity to collect statistical information about those who came to the site - what browsers, devices and operating systems they have.
• Automation. Sometimes developers can use such files to parse data. In this case, user agents are simply disguised as ordinary users so that they are passed through their filters by web servers.

Therefore, although the User Agent can be easily spoofed, it is recommended to use the usual values of this header. The User Agent itself cannot be used to identify the user. However, the user agent can become an additional hint to differentiate clients using, for example, one IP (NAT technology). Or, on the contrary, help in identifying the user in combination with other data.