User.js: help! need some test results: will take you two minutes

[Thorin-Oakenpants]

:star2: Attention all you watchers! If you have Windows 10, Linux or MacOS, I need your help for a couple of minutes

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css line height differs per platform in Firefox, and can thus be used to determine your os. It's not perfect, because I have found that if you change your default serif font and don't allow pages to choose their own fonts (document fonts = 0), then the font used will screw up the result. For example, I use Georgia as my default serif and locked doc fonts to 0 .. and I'm shown up as 19px (and everyone thinks I'm on Linux)

I've built a work-in-progress PoC, but need some more data. I'm just going off the original info supplied by hackerone - source, so I'm not even looking at san serif or monospace, or other fonts families, or styles (but I may do, this is interesting).

The other thing I have found is that something happened with the release of FF62, and all the measurements changed. Maybe it's something to do with stylo, IDK, and it doesn't matter - because I can 100% reliably detect your FF version based on internally how FF handles various JS features (you can't change these using prefs: if JS is allowed to run, I can detect your version in FF60 up)

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I need test results to confirm ESR60 and FF64/65

:exclamation: Make sure you allow document fonts for this test

• [SETTING] General>Language and Appearance>Fonts & Colors>Advanced>Allow pages to choose...

:exclamation: and don't zoom the page: do the test at 100%

So here is my little test page: https://thorin-oakenpants.github.io/testing/ and this is the bit of info I need from you guys ad gals

:small_orange_diamond: ESR60

| OS | expecting | confirmed result |
| -----: | :------------ | :--------------- |
| Windows7 | 19.2 or 20 | 20 |
| Windows10 | 19.2 or 20 | |
| MacOS | 19.5167 | 19.6833 (in a dodgy VM) |
| Linux | 19 | 19 (debian) 17 (debian 32bit) |
| Android | | |

:small_orange_diamond: FF64/65 preferably (or at least 62 or higher)

| OS | results |
| -----: | :--------- |
| Windows7 | 18 |
| Windows10 | 18, 19 (scaling=200%) |
| MacOS | 19.2, (19.6833 in a dodgy VM) |
| Linux | 19 (arch) 17 (debian) |
| Android | 19.5 |

Note: the test has two css line heights. One I specify to use the Times New Roman font: just paste both results. I am not sure what the default serif font is on other platforms, and if hackerone's test used the default font or specified one

...

[KOLANICH]

It may make sense to check with rfp on and off and usual ff vs tbb. And how about other engines?

Maybe it's something to do with stylo

stylo can be disabled in about:config.

I also wonder if these have changed because of a hardcoded value, or because of the same reasons font fingerprints change between versions.

[Thorin-Oakenpants]

RFP does not affect css line height .. don't really care about the cause of the change ... it's not a definitive os proof .. more for fun to show people that spoofing UA sucks donkey's balls

font fingerprinting per OS is much easier than this ... in fact it's downright easy AF

edit:

and usual ff vs tbb

TB is not the issue - I have that under control. They actually did modify this value, but now its off again. The point is that if TB breaks the test, that's good. I want to show what happens when it's not protected (which is moot since it's too easy to get OS anyway)

[crssi]

Win 10, FF 64.0.2 x64

firefox version | 64
-- | --
css line-height | font size: 16px, line height: 18px
[times new roman] css line-height | font size: 16px, line height: 18px

[Thorin-Oakenpants]

^ thanks

[yssmcl]

Arch Linux, Firefox 64.0.2:

firefox version                   64
css line-height                   font size: 16px, line height: 23px
[times new roman] css line-height font size: 16px, line height: 19px

[Thorin-Oakenpants]

^^ thanks :kiss:

[theontimetechguy]

Mac OS 10.12.6

firefox version | 64
css line-height | font size: 16px, line height: 19.2px
[times new roman] css line-height | font size: 16px, line height: 19.6833px

ESR

firefox version | 60
css line-height | font size: 16px, line height: 19.2px
[times new roman] css line-height | font size: 16px, line height: 19.6833px

[Thorin-Oakenpants]

^^ oooh .. nice

edit: not sure why a ESR60 returns the new value, but seems MacOS returns more than one decimal point

[1xPdd]

Debian, FF 64.0.2 (64-bit)

firefox version 64
css line-height font size: 16px, line height: 23px
[times new roman] css line-height font size: 16px, line height: 17px

[Thorin-Oakenpants]

^^ thanks :kiss:

[grauenwolfe]

macOS 10.12.6

firefox version 62
css line-height font size: 12px, line height: 13px
[times new roman] css line-height font size: 12px, line height: 13px

[Thorin-Oakenpants]

thanks @grauenwolfe - that seems low. Can I ask if you have retina display? Or if you have a dpi other than 96? Also that you allow pages to set their own font (just for the test). TIA :kiss:

[Thorin-Oakenpants]

@grauenwolfe .and @1xPdd , can you redo your tests - a few days ago I inadvertently removed the css rules to enforce font size 16 on both and times new roman on the second

[grauenwolfe]

No problem.

First, yes, the pref to allow document fonts was changed for this. Was curious about the rsults so I relaunched FF and tested again with same results. Second, no Retina Display used, this was with an NEC PA302W monitor which has the following:
aspect ratio: 16:10
resolution: 2560 x 1600
ppi: 101

Can run it on the Macbook Pro that _does_ have Retina Display if you want.

[grauenwolfe]

New test:

firefox version 62
css line-height font size: 16px, line height: 17px
[times new roman] css line-height font size: 16px, line height: 19.2px

[Thorin-Oakenpants]

Can run it on the Macbook Pro that does have Retina Display if you want.

Might be interesting :) I know who to call for my retina display detect testing then

[1xPdd]

21-inch 1920x1080 screen, if that matters

firefox version 64
css line-height font size: 16px, line height: 23px
[times new roman] css line-height font size: 16px, line height: 17px

[Thorin-Oakenpants]

^ bump ... come on guys .. 900+ stars .. 90 odd watchers .. can we get some MOAR results - especially non-windows

[Marc05]

W10x64 (system scaling set to 200% if it matters)
firefox version 64
css line-height font size: 16px, line height: 19px
[times new roman] css line-height font size: 16px, line height: 19px

[Thorin-Oakenpants]

^^ thanks @Marc05 :kiss:

[Thorin-Oakenpants]

that's a bit of a bummer, as 19px were kind of a linux thing. Does "scaling" change anything? And since the values didn't change, are you sure that Times New Roman was used? - TIA

[Marc05]

Setting the OS scaling to 100% produced the following results:

firefox version 64
css line-height font size: 16px, line height: 18px
[times new roman] css line-height   font size: 16px, line height: 18px

The setting mentioned in the OP is checked. Here is what it looks like at 200%:

Note that my native resolution is 2736x1824.

[theontimetechguy]

Running Firefox 60.4esr 32 bit
Linux raspberry 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2 (2018-10-27) x86_64 GNU/Linux

[Thorin-Oakenpants]

@theontimetechguy :kiss: I'll talk to you later .. get the lube handy

@Marc05 oooh, that's awesome. So scaling affects it. Which means the rules are still workable as a "best guess" (i.e no zoom, no scaling, probably no HiDPI)

[cy7yz2rj]

GNU/Linux (Debian)
60.4.0esr (64-bit)

firefox version | 60
css line-height | font size: 16px, line height: 19px
[times new roman] css line-height | font size: 16px, line height: 19px

[Thorin-Oakenpants]

thanks @cy7yz2rj :kiss: :beer:

[Thorin-Oakenpants]

thanks everyone ... I think I have enough info