Can I detect Tor Browser inside the browser itself, via Javascript I suppose?

Question

I\'d like to disable some features of a web app I\'m building, if the browser is Tor Browser. Can I inside the browser itself (client side, not server side) find out if the

Answer 1

The Tor browser is not designed to be undetectable (that's impossible to do). Rather, it is designed so that all copies are indistinguishable from each other: you cannot track a browser from one site to another, or from one visit to another, strictly through browser fingerprinting.

This gives it a distinct fingerprint of its own. As of right now, a browser that

1. Has a User-Agent of Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Firefox/31.0
2. Has a screen resolution that matches the browser window size (particularly if that size is 1000x800)
3. Has a time zone of "0" (GMT)
4. Has no plugins (navigator.plugins is empty)

is probably the TBB browser. The User-Agent string may change when the next ESR version of Firefox comes out, most likely to Mozilla/5.0 (Windows NT 6.1; rv:31.0) Gecko/20100101 Firefox/38.0.

The screen resolution/browser window match alone may uniquely identify TBB: even in fullscreen mode, there's a one-pixel difference between window height and screen height in Firefox.