Opened 14 months ago

Last modified 2 months ago

#30812 needs_information defect

cant modify browser default background color - about:blank, about:newtab

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


cant modify browser default background color - about:blank, about:newtab, about:config. nothing. Stuck with glaring white screen every time I watn to open a tab in tor browser. This needs to be resolved. I contacted firefox about this too. apparently this file userContent.css in the chrome folder under tor browser root profile folder, doesnt do anything. It works in latest firefox on windows 10, it doesnt eliminate white flash when loading a page, but at least newtab is dark when I open a new tab in FF. This issue isnt specific to me. its GLOBAL. If someone can find a solution would be appreciated.

@namespace url("");
@-moz-document url("about:newtab"), url("about:blank")

{ body {background-color: #000000 !important;} }

@-moz-document url(chrome://browser/content/browser.xul)

{ browser[type="content-primary"] {background-color: #000000 !important} }

Child Tickets

Change History (7)

comment:1 Changed 12 months ago by pili

Component: WebpagesApplications/Tor Browser
Owner: set to tbb-team

comment:2 Changed 12 months ago by mcs

Status: newneeds_information

I think this is caused by Tor Browser's anti-fingerprinting features. What happens if you use about:config to set ui.use_standins_for_native_colors to false? You may also need to set browser.display.document_color_use to 2. Note that it is not recommended to keep these changes because they may help a website identify you.

comment:3 Changed 12 months ago by Thorin

use this in a userChrome.css: tested and working in TB8*. There is no need to change settings that protect your fingerprint

@namespace url("");

/* about:newtab and about:blank
 * also remove white flash: see */
#browser vbox#appcontent tabbrowser,
browser[type=content] > html {
	background: #2A2A2E !important

EDIT: also tested and working in Firefox 68+ (for when TB is based on ESR68). Note, you will need to make sure toolkit.legacyUserProfileCustomizations.stylesheets = true

Last edited 12 months ago by Thorin (previous) (diff)

comment:4 Changed 12 months ago by Thorin

As a bonus, this also colors the letterboxing :)

comment:5 Changed 3 months ago by Thorin


RFP off

  • using the dark theme = about:blank was still white
  • hidden pref ui.systemUsesDarkTheme = 1 (1 = dark, 0 = light) = about:blank was dark

RFP on

  • RFP overrides prefers-color-scheme as light, and you get a white about:blank (i.e the above pref does not affect the fingerprint)


  • RFP interferes
  • pref is hidden and no UI

Solutions: as a first step

  • upstream get about:blank exempted from RFP - I assume this should be quite trivial

Note: there's a whole string of tickets and conflicts over OS theme vs Firefox theme vs prefers-color and the hidden override pref: and no consensus.

comment:7 Changed 2 months ago by Thorin

1634602 landed, but would need to be backported to ESR

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