[SOLVED] Unique tab ID appended to user agent string in Chrome for iOS?

Unique tab ID appended to user agent string in Chrome for iOS?

As I was testing my web app in Chrome for iOS (both iPhone and iPad), I noticed a weird ID appended to user agent string, e.g.:

    alert(navigator.userAgent)

would produce something like this (note the "3810AC74-327F-43D7-A905-597FF9FDFEAB" part at the end):

    Mozilla/5.0 (iPhone; CPU iPhone OS 5_1_1 like Mac OS X; en-us) AppleWebKit/534.46.0 (KHTML, like Gecko) CriOS/21.0.1180.77 Mobile/9B206 Safari/7534.48.3 (3810AC74-327F-43D7-A905-597FF9FDFEAB)

This ID seems to be tab specific and persists even when going to a different site.

My question is, if anyone knows anything about this and what it may be used for?

Update:

This GUID was appended to overcome the limitations of UIWebView. Kudos to eric for pointing this out in the comments.

Solution

That ID is not related in any way to tracking.

There is a chromium bug that goes into the details of why it is necessary: basically, it's needed in order to implement tabs.

From the bug tracker:

There is no API in iOS to know, in the network layer, from which UIWebView a network request is coming from.

[...] the solution [...] all the UIWebViews get the tabID (which is only local to the device) added to the user agent string.

You might also want to check a few twitter threads discussing this with further info.