[tor-bugs] #34007 [Community/Tor Support]: White Across Browser

[Tor Bug Tracker & Wiki]

#34007: White Across Browser
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 Reporter:  person130068           |          Owner:  ggus
     Type:  defect                 |         Status:  closed
 Priority:  Medium                 |      Milestone:
Component:  Community/Tor Support  |        Version:
 Severity:  Normal                 |     Resolution:  not a bug
 Keywords:                         |  Actual Points:
Parent ID:                         |         Points:
 Reviewer:                         |        Sponsor:
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Changes (by ggus):

 * status:  new => closed
 * component:  Webpages => Community/Tor Support
 * version:  Tor: unspecified =>
 * resolution:   => not a bug
 * owner:  (none) => ggus


Comment:

 Tor Browser in its default mode is starting with a content window rounded
 to a multiple of 200px x 100px to prevent fingerprinting the screen
 dimensions. The strategy here is to put all users in a couple of buckets
 to make it harder to single them out. That works so far until users start
 to resize their windows (e.g. by maximizing them or going into fullscreen
 mode). Tor Browser 9 ships with a fingerprinting defense for those
 scenarios as well, which is called Letterboxing), a technique developed by
 Mozilla and presented in 2019. It works by adding white margins to a
 browser window so that the window is as close as possible to the desired
 size while users are still in a couple of screen size buckets that prevent
 singling them out with the help of screen dimensions.

 In simple words, this technique makes groups of users of certain screen
 sizes and this makes it harder to single out users on basis of screen
 size, as many users will have same screen size.

 https://support.torproject.org/tbb/maximized-torbrowser-window/

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/34007#comment:1>
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