In the world of web, User Agent is a program or software existing inside a browser or in a program that tells the internet (server,website) some information about you. I mean information about your browser, your operating system, your computer or device information etc.
Then the internet or a website you are connecting to understands, identifies your device and software, so the server can optimize the website or content for you for better viewing.
For example, when you are connecting to a website (example – Facebook ) through a mobile device, the server will identify that you are accessing the website through a mobile device and it will then respond with the mobile version of the website that is optimized for mobile devices and easy to use, this is possible only because user agents
To see the difference, try to load a website, lets use Facebook.com to test this, first load Facebook on your computer browser, then next, load it in your mobile device browser. What did you see? Do you see a different version of Facebook that is large and wide in computer – but small and optimized in mobile device? That is user agent in play here.
When you are loading Facebook on a mobile device, the Facebook server understands “oh, this guy is on a mobile device, so i must respond him with the mobile version of Facebook, if i didn’t, the whole thing will be messy on his small screen“.
Because mobiles have different user agents, computers too have different user agents. When a device connecting to the internet or website, to be specific, the device sends information about itself. like i mentioned above. that is user agent
Is it possible to change a user agent?
with the right tool, you can change your user agent and make the websites think that you are on a different device than you actually are.
For example, most mobile web browsers have an option called “Request Desktop Site“, what this option do is simply switching the user a gent, to a desktop user agent, so you can view the desktop version of the website in your mobile device.
This is useful if some functions and options of a website isn’t available on mobile devices.
I hope i was able to explain user agent to you. 😉