6 ms·

Why does a website need to know my zoom level, i.e., why is this information even made available?

by chmars 5y ago

3np 5y ago
It’s been a while but IIRC as long as there’s JS it can be gotten implicitly by probing and comparing dimensions of elements and viewport on the page. We could question if that’s really necessary as well but the ship has kind of sailed on that one.
- egeozcan 5y ago
  IMHO, even when sand-boxed, allowing a fully Turing-complete language with such a vast selection of available APIs to run on page load per default is what kills privacy. People should be trained to allow script execution only when they trust the site, and there should be levels: Zero, Fully Isolated, Trusted. OK now time to wait for someone to tell me this will be too much to ask from users. It wouldn't be an invalid point either, we can't even train people to have some common sense when in control of tons of steel going fast loaded with highly flammable liquids... So, there's that. I don't know.
  - HWR_14 5y ago
    It's not even per page. I don't care if I trust that page, I don't want any FB scripts to run. There are so many external libraries included (loaded from a CDN they do not control) that I don't trust any developer to know with 100% certainty what their app includes.
- CapsAdmin 5y ago
  Maybe something like randomizing the variables in a realistic way across many sessions where the real session is controlled and viewed directly by the user. I don't think it would work when there's a state across views or server though, but maybe that's something you avoid when using Tor anyway?
romeovs 5y ago
My hunch is that it’s not explicitly provided to the website by the browser, but there are ways to measure what the zoom level is using JavaScript on the page. One could use element.getBoundingClientRect and similar APIs to measure what size certain elements are rendered at and compare that with their default size for instance. The resulting zoom level can then be used as a signal for fingerprinting.
no_way 5y ago
To render content based on device screen scaling. window.devicePixelRatio provides page zoom level combined with OS DPI setting. Things like canvas do not use scaling by default, so to render content appropriately you need to know by how much you have to scale it. Other use cases exit too.
deleted 5y ago
[deleted]
BLKNSLVR 5y ago
I find that question valid for almost everything that's used for fingerprinting. Eg. Why is timezone available by default? I wrote more but I sound like old man shouts at cloud. I've got ad and JavaScript blockers, but so much of the web is created sitting upon a mesh of invasive bullshit that it breaks easily. Shakes fist at cloud anyway.
- asddubs 5y ago
  so that dates displayed can be correct by default, without having the user select their timezone from a dropdown with a million different options
  - Folcon 5y ago
    Why not offer the "dropdown" at a layer the browser manipulates? IE, web component where you can set a format string and then the browser renders it substituting the info it has? Then sites that need to know the date can ask for it. There's a lot we could do by splitting stuff into permissions and some sort of standard templates.
    - asddubs 5y ago
      and then you can read it out to indirectly get the time zone anyway (albeit a less specific version of it, since you wouldn't have the DST info). also, sometimes you need to actually have the users time zone for things like e.g. scheduled blog posts, so that they will show up when the user expects them to, not their scheduled time in UTC or whatever. I use a site that only does UTC, and time zone related complaints are the most common issue asked about on the forums
    - peoplefromibiza 5y ago
      > IE, web component where you can set a format string and then the browser renders it substituting the info it has? you can easily detect this - please display this localdatetime as a string - read it back and parse it - are they (almost) exactly multiples of 60 minutes apart? - if yes it's most probably your timezone
puregram 5y ago
southerntofu 5y ago
This is the problem with the modern web, which has become an app distribution platform. When you treat the browser as an OS, you need to expose a lot of information for stuff to work. It would be very interesting to develop a modern web based purely on declarative content (modern HTML/CSS). HTMX is an interesting take on this, although it's currently implemented as server-provided JS: i don't see a reason why such patterns couldn't be implemented by the browser itself.
- foxfluff 5y ago
  > It would be very interesting to develop a modern web based purely on declarative content (modern HTML/CSS). For sure. I think some scripting could also potentially be implementable without massive fingerprinting / privacy implications. E.g. pure compute scripts, form validation, etc. that has no practical way to smuggle any data out of your browser. Anything that sends a request would have to be statically derived (or explicit user input as into form).
  - southerntofu 5y ago
    Functional data pipelines without side-effects could do the trick indeed. It would also make it a lot easier to debug for performance issues, and the browser could be more clever about optimizations: for example if you've got a loop changing DOM elements, maybe you could wait for the loop to finish before starting a re-render... something that's impossible to do with JS-based rendering where global page state may change under your feet at any given time. EDIT: Just for the sake of mentioning, simple/obvious computations for interactivity was the promise of GNU's libreJS project. I'm unaware of the current state of it, though.
- mdp2021 5y ago
  > It would be very interesting to develop a modern web based purely on declarative content Is not that the subset of the web that would work when javascript is disabled? Some already develop it in that direction - what is not declarative shall be unnecessary. Or are you suggesting something different?

Why does a website need to know my zoom level, i.e., why is this information even made available?

by chmars 5y ago

Why does a website need to know my zoom level, i.e., why is this information even made available?

3np 5y ago

It’s been a while but IIRC as long as there’s JS it can be gotten implicitly by probing and comparing dimensions of elements and viewport on the page. We could question if that’s really necessary as well but the ship has kind of sailed on that one.

egeozcan 5y ago
IMHO, even when sand-boxed, allowing a fully Turing-complete language with such a vast selection of available APIs to run on page load per default is what kills privacy. People should be trained to allow script execution only when they trust the site, and there should be levels: Zero, Fully Isolated, Trusted. OK now time to wait for someone to tell me this will be too much to ask from users. It wouldn't be an invalid point either, we can't even train people to have some common sense when in control of tons of steel going fast loaded with highly flammable liquids... So, there's that. I don't know.
- HWR_14 5y ago
  It's not even per page. I don't care if I trust that page, I don't want any FB scripts to run. There are so many external libraries included (loaded from a CDN they do not control) that I don't trust any developer to know with 100% certainty what their app includes.
CapsAdmin 5y ago
Maybe something like randomizing the variables in a realistic way across many sessions where the real session is controlled and viewed directly by the user. I don't think it would work when there's a state across views or server though, but maybe that's something you avoid when using Tor anyway?

romeovs 5y ago

My hunch is that it’s not explicitly provided to the website by the browser, but there are ways to measure what the zoom level is using JavaScript on the page. One could use element.getBoundingClientRect and similar APIs to measure what size certain elements are rendered at and compare that with their default size for instance. The resulting zoom level can then be used as a signal for fingerprinting.

no_way 5y ago

To render content based on device screen scaling. window.devicePixelRatio provides page zoom level combined with OS DPI setting. Things like canvas do not use scaling by default, so to render content appropriately you need to know by how much you have to scale it. Other use cases exit too.

deleted 5y ago

[deleted]

BLKNSLVR 5y ago

I find that question valid for almost everything that's used for fingerprinting. Eg. Why is timezone available by default? I wrote more but I sound like old man shouts at cloud. I've got ad and JavaScript blockers, but so much of the web is created sitting upon a mesh of invasive bullshit that it breaks easily. Shakes fist at cloud anyway.

asddubs 5y ago
so that dates displayed can be correct by default, without having the user select their timezone from a dropdown with a million different options
- Folcon 5y ago
  Why not offer the "dropdown" at a layer the browser manipulates? IE, web component where you can set a format string and then the browser renders it substituting the info it has? Then sites that need to know the date can ask for it. There's a lot we could do by splitting stuff into permissions and some sort of standard templates.
  - asddubs 5y ago
    and then you can read it out to indirectly get the time zone anyway (albeit a less specific version of it, since you wouldn't have the DST info). also, sometimes you need to actually have the users time zone for things like e.g. scheduled blog posts, so that they will show up when the user expects them to, not their scheduled time in UTC or whatever. I use a site that only does UTC, and time zone related complaints are the most common issue asked about on the forums
  - peoplefromibiza 5y ago
    > IE, web component where you can set a format string and then the browser renders it substituting the info it has? you can easily detect this - please display this localdatetime as a string - read it back and parse it - are they (almost) exactly multiples of 60 minutes apart? - if yes it's most probably your timezone

puregram 5y ago

southerntofu 5y ago

This is the problem with the modern web, which has become an app distribution platform. When you treat the browser as an OS, you need to expose a lot of information for stuff to work. It would be very interesting to develop a modern web based purely on declarative content (modern HTML/CSS). HTMX is an interesting take on this, although it's currently implemented as server-provided JS: i don't see a reason why such patterns couldn't be implemented by the browser itself.

foxfluff 5y ago
> It would be very interesting to develop a modern web based purely on declarative content (modern HTML/CSS). For sure. I think some scripting could also potentially be implementable without massive fingerprinting / privacy implications. E.g. pure compute scripts, form validation, etc. that has no practical way to smuggle any data out of your browser. Anything that sends a request would have to be statically derived (or explicit user input as into form).
- southerntofu 5y ago
  Functional data pipelines without side-effects could do the trick indeed. It would also make it a lot easier to debug for performance issues, and the browser could be more clever about optimizations: for example if you've got a loop changing DOM elements, maybe you could wait for the loop to finish before starting a re-render... something that's impossible to do with JS-based rendering where global page state may change under your feet at any given time. EDIT: Just for the sake of mentioning, simple/obvious computations for interactivity was the promise of GNU's libreJS project. I'm unaware of the current state of it, though.
mdp2021 5y ago
> It would be very interesting to develop a modern web based purely on declarative content Is not that the subset of the web that would work when javascript is disabled? Some already develop it in that direction - what is not declarative shall be unnecessary. Or are you suggesting something different?