Opened 15 months ago

Last modified 7 months ago

#30625 new defect

new window dimensions are affected by dpi

Reported by: Rick Owned by: tbb-team
Priority: Medium Milestone:
Component: Applications/Tor Browser Version:
Severity: Normal Keywords: tbb-fingerprinting-resolution
Cc: Actual Points:
Parent ID: Points:
Reviewer: Sponsor:


I read the other tickets, which all relate to enabling the toolbar.
But my Tor Browser also deviates at default, so I decided to post it as well.

I have verified these results with a fresh install of Tor Browser 8.5
The detected resolution is 1004x801. (with toolbar it's 1004x796)
Any further info you need?

I would like to know, if this is "normal" (given the toolbar/resize bug), and all users have it. Or if not, I wonder what the cause might be (what I can do to fix this). Obviously I am in a bit of a panic, afraid this makes my fingerprint unique among Tor users, and has been potentially doing so for a long time.

Child Tickets

Change History (8)

comment:1 Changed 15 months ago by Thorin

Any further info you need

What is your OS? If Linux, what is your desktop environment/gtk?. What is your theme (did you change it to dark or light)? What is your theme density? Did you toggle on the menu bar?

I've been tracking this since FF57, and have a lot of setups here. I will see if I can replicate (both TB and ESR60.0.7)

Edit: Did this only start happening with 8.5, or did you only just notice it: i.e did this happen on 8.0.9?

Last edited 15 months ago by Thorin (previous) (diff)

comment:2 Changed 15 months ago by Rick

default theme
default density
no menu bar

Switching to either "Compact" or "Touch" density changes the value to 1004x802.
Switching the theme has no impact.

I've been using, and auto-updating, the browser for a long time. I cannot say when the problem started (which is part of my panic).
My memories on browser version for this week are actually very strange and confusing.
But I think the most logical assumption would be, that the update to 8.5 "motivated" me to do the first test (changes to UI). In which case I did not test with 8.0.9, no matter what my memories would make me think.

If I had access to installs of older versions, I'd gladly test them all.

Last edited 15 months ago by Rick (previous) (diff)

comment:3 Changed 15 months ago by Thorin

I have Windows 7 right here, and cannot replicate. What's your display at: Control Panel\Appearance and Personalization\Display

Older versions are here:
When testing, just unpack/install it to a temp directory each time. e.g

  • c:/tortest/756
  • c:/tortest/90a1

You could try a 7.5.6:
Or a 9.0a1

Just run one at a time. See if existed last ESR (7.5.6), and the next ESR (9.)

What happens if you do a new clean install of 8.5, e.g to c:/tortest/85/ ?

Last edited 15 months ago by Thorin (previous) (diff)

comment:4 Changed 15 months ago by Rick

From the moment I read it, I knew it was the DPI setting (fuzzy memory).
Both 7.5.6 and 9.0a1 didn't resize properly with a custom DPI setting.
There were some patterns to the deviations, but I think these values alone may create a unique fingerprint.

I didn't test and write down all combinations, but I did a lot (not sure if there is any value to those notes).

I found 3 exceptions when testing 9.0a1 @150% DPI.
With enabled Titlebar + Normal or Compact Density: 1000x600
With enabled Titlebar, Menubar, and Touch Density: 1000x500

Otherwise it is just combinations of DPI and UI elements somehow creating different values of +- a few pixels.
Only DPI@100% without the Bookmarks Toolbar delivered correct results on 9.0a1.

comment:5 Changed 15 months ago by Thorin

I'm not sure if these few pixel issues will ever get sorted. The good news is that in 9.* there is a feature called letterboxing which solves a lot of problems. It means any changes to the chrome (such as maximizing, going fullscreen, manually resizing, toggling on sidebar/toolbars/menubar, etc) will no longer cause issues. Edit: and of course, regardless of the browser's actual inner window, e.g from bugs/DPI/density, the web content will be letterboxed into the a limited set of sizes

The pref is currently hidden in TB9, it is privacy.resistFingerprinting.letterboxing, you create it (boolean) and set to true. Try it in your 9.0a1. Open the browser, load a web page. You'll see what I'm talking about. It currently steps in 200w by 100h

Or load and as you resize keep an eye on the [css] inner window result.

Last edited 15 months ago by Thorin (previous) (diff)

comment:7 Changed 7 months ago by Thorin

Summary: (without toolbar) the window size is not exact multiple of 100 pixelsnew window dimensions are affected by dpi

comment:8 Changed 7 months ago by Thorin

#21341 is a duplicate

Note: that ticket says this issue started with 6.5

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