The User-Agent is a software used by an user (Thanks Captain). In this article, we'll talk about web browsers.
Some User-Agent in the wild
When you are wandering, you don't know it but you tell every website which web browser you are currently using. But it's not clear and simple nor very logical.
If you use Firefox you won's send Firefox 77, no no. Instead you are sending Mozilla/5.0 (Windows NT 6.1; WOW64; rv:77.0) Gecko/20190101 Firefox/77.0
It's not ultra obvious but it's basic informations. It tells the web server which OS you are using, which browser and it's rendering engine. It's quite logical.
If you use Safari on a Mac, here is what you may send : Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit/537.75.14 (KHTML, like Gecko) Version/7.0.3 Safari/7046A194A . It's getting messy with nearly half the information wrong or just not up to date but still present.
If you are one of those most evil users relying on the real Chrome on Windows you'll send this :
Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko)
You want to laugh a bit ? Here is what a modern Edge (a browser from a small startup) : Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.102 Safari/537.36 Edge/18.19582 . Over the top ! What will we get in 20 years ?!
But why ?
If you wonder why do browsers identify themselves like this you would have to go back in time. Not so long ago, many websites used tricks to build their pages instead of using standardized components. So to display correctly, they tried to detect browsers and adapted their content based on this information.
But web browsers evolved quite fast and mimicked each other, so they tried to guess the logic behind the detection to trick the website to force them to send the content for another browser… It escalated…
So what ?
I already wrote a blogpost (in french, sorry) about this here. So why another one ? Just because i like to write (true story).
I chatted about this on IRC the other day, so i wanted to know. In the blogpost, I finished with a Norman answer : "maybe yes, maybe no" to the question “Can web browser be honest and send a simpler User-Agent String ?” So, i wanted to try to answer this.
I configured my web browser (the mighty Qutebrowser ) to send a custom string : Qutebrowser. Only this, no convoluted things.
Will it browse ?
Guess what ? Everything works.
Everything ? No ! Somewhere on the World Wild Web lies a small company providing some websites refusing to adopt best practices about web development. You may have heard of these websites.
There is Youtube which is a small site providing multimedia content. There is also Google Maps a web mapping service. We should forgive this small team of devs trying to do their best to stay relevant in this fast moving world.
I'm not saying that every other website works perfectly, but it's been one week of daily browsing and i didn't encounter any other website behaving strangely due to this user-agent.
When using Youtube, its look is a bit different. It looses the dark mode and the livechat for videos providing it. With the exact same web browser with just its real user-agent string, it works perfectly. So, it's not the browser behaving badly, it is just the website being coded like this. They may just be not skilled enough or their intentions are maybe a bit evil. In Google Maps, i loose the ability to display the 3D satellite view. Coming from the biggest company on the web, which also make the most used browser, is it really incompetence or malice ?
What do I do now ?
I'll keep my honest custom user agent string and will lie to Google only. If you want to do the same with Qutebrowser :