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Re: [tor-talk] TorBrowser spoofed screen size?

Following up on inconsistency of spoofed TBB screen sizes, shown on test sites: I did more testing / checking. Then posted comments on Trac https://trac.torproject.org/projects/tor/ticket/7256#comment:10 & comment #11.

For me, with each browser fully maximized, there's a *fundamental difference* in what the test sites see for "screen size" of regular Firefox (27), VS. TBB 3.5.2. Same monitor, same displayed toolbars (of nearly identical heights) in both browsers - but vastly different "screen size" detected.

This would SEEM to make TBB users stick out like a sore thumb!? It seems to be a large problem, *regardless* of the system DPI setting (default, or custom value).

"Additional comment: note that at the same moment Panopticlick, etc., is showing an odd screen size for TBB 3.5.2 (like 1920 x **966** OR, if refresh page once, perhaps 1920 x **967**), a full screen capture of the same maximized browser screen (taking up full monitor), shows 1920 x **1080*.*

The "966 or 967" TBB screen height (or whatever odd number),**turns out to be** the height for the part of browser window, beginning just below the browser navigation bar, down to the top of "Addon Bar."

However, in regular Fx with exact same, similarly sized toolbars displayed (as in TBB), the test sites show screen size of the **full** monitor: 1920 x **1080**, not just the "usable display area" of the browser pane (the part of browser window where websites actually display)." "I see "odd" (unique) screen sizes reported / detected on browser test sites, in TWO scenarios.
1) When Windows system DPI is set = default 96 DPI.
2) When system DPI is NOT the default value (many users must set it larger, to be able to read screens. Ex.: both Windows' & apps' Help screens, or text in browser screens (TBB).

On browserspy.dk or others, with **Windows' DPI = 96**, AND the TBB UI maximized (full screen), test sites don't show "common" screen (monitor) size. They show something like 1920 x 927 - a very "odd" value.

At same exact time, regular Fx shows "screen size" = **1920 x 1080** x 24."

On 3/6/2014 8:21 AM, Joe Btfsplk wrote:
On 3/6/2014 1:59 AM, Georg Koppen wrote:
Joe Btfsplk:
But, EVEN WHEN  I reset my system to 96 DPI, reboot - TBB still shows a
weird value - like 1920 x *933* (just an example).
NO one has a screen size w/ those odd numbers.  That's the issue.
Yes, they should be a multiple of 200 x 100. Resizing the browser window
does currently not take DPI and the size of taskbars into account (this
is #9268). See my comment 7 there as well that was probably for you.
Thanks Georg, but I think? we're talking about different things.

The bug #9268 is about the size of TBB window when it's launched
(whether it fits on monitor, etc.).

The issue in THIS post, is the "screen size" (monitor size), that can be
detected by sites for fingerprinting purposes as opposed to how well the
TBB UI fits on the monitor when it's 1st launched.  Not the same things
- though possibly ? related.

On the browser test sites mentioned, I'm not running the tests w/ TBB
window partially enlarged (as when 1st launches).
But to clarify / add to your comment here, IF... one DOES run the
browser tests w/ TBB UI in "non-full screen mode," the test sites will
show *different* detected screen size than when it's maximized.

And, if you zoom the TBB screen (Ctrl + scroll), the test sites detect a
different "screen size," as well.
Different issues than my original question on this post, but worth noting.

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