https://news.ycombinator.com/item?id=35243355

The take-away I got from this article is that, companies found a way to uniquely identify you anyhow, without cookies.

Is this too little too late?

FF does some good things to work around fingerprinting, although simply using FF puts us in a pretty small (marketable) group in the first place.

In particular, User-Agent strings are now a net-negative. I've never run into a website that doesn't work on Firefox. I do occasionally run into websites that claim to not work on Firefox. We software developers have shown that we can't be trusted with information pertaining to what browser someone is using, and as such should have the privilege taken away. If you're reading this, and you have access to a codebase that reads User-Agent strings for anything more than idle curiosity, just delete it and push to master.

I have a canvas element where the user needs to be able to both scroll and zoom with the mouse wheel. Generally, zooming involves scrolling while also holding the ctrl button down - except on MacOS, where it's cmd. I obviously want to use the operating system conventions that my users will be expecting, but the best way of determining that, that I've found, is searching for the string 'Mac' in the user agent string.

Like I say, if you know of a better way to detect whether I should be binding on ctrl or cmd, let me know! This is the first time I've used the user agent in a long time, and it feels like there should be a better system...

https://www.bitestring.com/posts/2023-03-19-web-fingerprinti...

But you are right, it's likely that there are other ways other than cookies and fingerprinting that companies can track you.

Uncommon settings being exposed to websites makes fingerprinting much more reliable.

You could potentially try and "execute" all possible declarations at the same time, in effect just loading every URL or image declared in the CSS file at once, so the server can't tell which path was actually used. But (a) this would itself be identifiable as an anti-tracking measure (which can contribute to a fingerprint), and (b) this loads a lot more data in the general case, which is exactly what browsers want to avoid.

The more people identified as having anti tracking on, which should be the default, the less useful that bit of tracking is.

One would generally expect that both paths produce different outcomes, because this is the purpose of media queries, to produce different appearances for different screens. In the example about light mode vs dark mode, a well-designed, non-fingerprinting CSS file might well load different background images for an element to match the user's theme - a dark-background image for dark mode, and a light-background image for light mode. This is the sort of behaviour we are aiming for with this feature.

The problem is that this good behaviour is indistinguishable from more malicious behaviour where the images are only used to do fingerprinting. And FWIW, this is the simplest way of doing fingerprinting that I could think of. In the general case, it is not possible to detect whether a given media query would be fingerprintable by a server. For example, a given media query might increase the height of a particular element, pushing a lazy loaded image below the fold and causing it to not be requested immediately, but only after a few seconds when the user scrolls down to it. Or instead of having one "homepage" link on the page, you have multiple, but you only show one depending on which media query fits best. Then, as soon as the user clicks the "homepage" link, you know which link was visible to them and can fingerprint them accordingly.

Which is why the nuclear option here is just turning off all possibilities for existing a user's unique preferences, because it's the preferences themselves that are being used to fingerprint the user.

I don't want websites to follow my settings; I want my browser to follow my settings, overriding or ignoring what the website says if necessary. I don't see why the browser has to tell the website what it's overriding or ignoring.

For example, with the dark mode/light mode "attack", the browser will download the necessary HTML and CSS in as unidentifiable a way as possible, but then it needs to render that for your machine. But the CSS file might contain a media query line that says something like "if the user wants dark mode, load this dark image as a background for this element". And to correctly respond to the query, the browser then needs to send another request to the server to download that image, that effectively indicates whether the user is using dark mode or not.

This principle can be used to detect a lot of your user settings. For example, your zoom level will effectively change how wide the browser window appears to be from the perspective of a CSS file*, which means that it's possible to use more media queries to detect that. Likewise a lot of accessibility queries like prefers-reduced-motion, while really useful for many people, can be used alongside other information to create your unique browser fingerprint.

This is just with HTML and CSS. If you add Javascript to the mix, it's even easier to fingerprint you based on various settings.

* there are technically other ways of performing zooming that wouldn't necessarily be visible, but they have poor usability. For example, you could have the classic PDF-style zoom where the PDF is rendered in a fixed size, and the user simply views a small, viewport-sized portion of the file. But this is a pain if you want to read text that's wider than your screen, because now you need to scroll back and forth. The browser approach allows text to be reflowed to match the viewport width, but this reflow will always be observable, and therefore can always contribute to a fingerprint.

If the browser insists on doing those things, yes. But why does the browser have to do that?

For example, if I set privacy.resistFingerprinting = true, why can't the browser just locally have a "light mode" and a "dark mode" that does the best it can to render the site locally in those modes without making any additional requests that it didn't already make for the default version of the page? Yes, I'm sure the website designer has lots of wonderful stuff to customize the look and feel in those modes--and I might like that if I could be sure that the website wasn't also using that stuff to fingerprint me. But if I'm telling my browser to resist fingerprinting, clearly I don't trust that website, so why would I want all of its customizations for light mode/dark mode?

Alternatively, everywhere where you have a link, you could have one link for each combination of bits that you want to send to the backend. Then using CSS, you can hide or display this links so that only one version of each link is displayed at a time, and then monitor what gets clicked. If the user clicks the link that says `/?dark-mode=true&orientation=vertical`, you now know two extra bits of information.

This is obviously all excluding Javascript, which can just read this information straight out and use it.

The problem ends up being that there's so many different (and often valid) ways to customise a website that it's very difficult to limit these customisations to only the "safe" ones. Even if the only properties I was allowed to use were colour/background-color, I'm sure I could come up with some sort of way to use them to convey information. So the only safe option here is to turn off the customisations altogether. Yes, it's still possible to track if a user is using light mode or not, but now they're all using light mode, so that bit of information becomes useless.

It's not just an "optical" zoom.

But more directly, zooming can put you in very nonstandard width x height dimensions. Carrying those dims across different pages makes for an easy fingerprint which is probably why it's reset.

I don't care what the website's JS/CSS says. At the end of the day the browser has a rendered canvas; I just want to zoom the canvas (and clip it at the window dimensions, providing scrollbars if necessary, if zooming makes it larger than the window dimensions). The browser shouldn't have to re-run anything to do that; zooming and clipping a canvas are graphics operations that have existed in computers for as long as there have been computers with graphics at all.

When people are in a browser and expanding the content they want the content reflowed - having to scroll to read the width of a line is super obnoxious, and makes reading text much harder. This is made even more frustrating when you recall that a lot of time the reason for zooming is to make things easier to read.

There are very few times where the correct response to "increase the zoom" is simply an affine transform of the rendered content, from both a usability standpoint or from user intent.

Even if this is the case, I don't see why the browser has to re-run anything from the website or tell the website anything. It can just do the reflow operation locally. Yes, the central data structure then is the DOM rather than a rendered canvas, but the DOM is still held locally.

What are you concerned is happening?

Then why does the zoom level reset itself to 100% every time I reload the page if I set privacy.resistFingerprinting = true?

> What are you concerned is happening?

I'm concerned that setting privacy.resistFingerprinting = true breaks a feature (that my browser remembers the zoom level for a given site so I don't have to reset it every time I reload that site) that should, as you say, be "entirely local".

The issue is not related to page loads, and layout behaviour is not impacting or causing differing load behavior.

First we need to consider what the goal of fingerprinting a browser is, and subsequently how that is done. The goal is not just "track a user", it is "track a user without using any explicit storage", so no cookies, client storage, etc. So instead all that a fingerprinting service can do is read implicit data from the browser, and using a collection of that data construct a unique ID. Most data that you read will be the same across large numbers of browsers: user agents, installed fonts, etc so what you do is build up a signature from those properties that vary from the mean. If you query enough different properties that hope is that you can accumulate enough variation to create a unique (-enough?) identifier that persists for that user.

Which gets us to your feature. The enormous majority of users have default zoom. So if your browser presents a different zoom level that provides a large amount of information to uniquely fingerprint you.

Hence `privacy.resistFingerprinting = true` disables non-default zoom on load, because it's directly finger-printable.

Does that make it more clear what's going on?

No. I already understand why non-default zoom gives websites a way to fingerprint you, if your browser insists on telling the websites that you have a non-default zoom level.

What I don't understand, and what nobody in this discussion has been able to explain, is why a browser with privacy.resistFingerprinting = true can't just lie to the website about what the zoom level is. You have said that zoom should be a local operation; that means the browser shouldn't have to tell the website anything about the actual zoom level if the user doesn't want it to. It should just load the page, telling the website whatever default things it tells the website when privacy.resistFingerprinting = true, including, presumably, a default zoom level, and then do the local zoom operation afterwards.

However, browser zooming incurs layout logic. It's no different that resizing the browser viewport. Code is run on the site (whether CSS or JS) to determine how the site should render at that size.

CSS/JS is run even when loading the site in the first place. There is nothing special about zooming, so it's like asking why layout code has to be run when you visit a site.

Well, you can turn off JS and CSS styling, but that's too hamfisted for most people.

Here's how a site can load different stylesheets depending on viewport width:

    <link rel="stylesheet" media="screen and (min-width: 601px)" href="desktop.css" />
    <link rel="stylesheet" media="screen and (max-width: 600px)" href="mobile.css" />

Any idea how they would do that?

I also tried setting privacy.resistFingerprinting = true in Firefox, but it's sad to see that most websites become unusable (most sites using canvas just render a green/purple mess), zooming in Google Maps is basically broken (skips several levels at a time), and like others have mentioned dark mode and time zones also stop working.

What a mess the (somewhat private) web is nowadays. The more I think about it, the more I am convinced legislating privacy is the only way out of this arms race we seem to be losing.

EDIT: Sorry, the parent post already included fingerprinting, missed that. Rant still stands though :)

> we never do cross-domain tracking.

Not sure if that is true though...

[1] https://fingerprint.com/pricing/

Also, there are some major drawbacks, like your browser setting UTC as the default timezone. That one has caused some mix ups when filling out Doodles.

I recently noted that they display some of my browser settings as used by 200.3% of their users. And many other figures over 100%. And they offer positions with a deadline last summer.

As far as fingerprinting issue, Brave again does a better job than most, again as a default:

"If you need to use Chromium, then Brave browser is a good choice. It also randomizes fingerprint for each session, making it harder to link your browsing sessions."[1]

[1]https://www.bitestring.com/posts/2023-03-19-web-fingerprinti...

Makes me wonder how much of this is real improvement vs. publicity.

Separate cookie jars don't prevent data brokers from correlating cookies from a common IP + user agent pair. The only solution is to block third parties altogether.

Worse, it may actually make you more identifiable because a Chrome on Linux user agent with the TCP fingerprint of Windows and TLS fingerprint of Firefox is going to stick out like a sore thumb, even more than a rare-but-at-least-consistent fingerprint with no trickery.

For your IP+UA hypothetical, the easy fix is to make everyone look the same. IP should be the only personally identifiable factor. Tor and desktop Firefox w/ privacy.resistFingerprinting turned on both do this. Open window not-maximized at 1000x1000 size, use the same UA regardless of what platform & browser version you're actually on, and a bunch of other stuff. That said, I don't know how effective it actually is against modern comprehensive fingerprinting libraries.

On a side note: Isn't it odd, how the composition of different technologies (here HTTP and DNS) make it unintuitively complex to implement a so intuitively natural policy as "every website gets to read only its own cookies"?

That's already the case, isn't it? It's just that embedded parts by a 3rd party can set their own cookies, which can be read by the 3rd party whenever it is embedded in any other page.

1: https://en.wikipedia.org/wiki/HTTP_cookie#Third-party_cookie

You are calling all of the assets loaded, no matter from where, as one “website”. The person you are replying to considers each domain for each asset on the single page as being different “websites”

You can see which browsers partition state (and which don't) in the State Partitioning section of https://privacytests.org. Firefox passes nearly all of those tests because Total Cookie Protection is enabled by default.

I'm not sure what document.referrer blocking is meant to accomplish - if the intent is for the referrer to pass information to the loaded site then they can just include that in the url. If the intent is "don't let people know where you saw the link", then sadly there are plenty of sites that gate access on the referrer and they get broken. The fact that no one is filtering that kind of indicates the cost/reward balance.

Calling "media queries" a privacy issue is absurd: literally the purpose of these is to allow sites to tailor to the view format. More over you can directly measure these from JS, it's just less efficient and more annoying.

The "known tracker" blocking is more curious as I'm unsure how that's expected to scale, nor what happens if a browser ever misclassifies one (be it a resource or a query parameter). Certainly query strings can be trivially changed to make anything a major browser does just break instantly, and similarly trivially changed to not be statically identifiable.

I also wonder how those are tested because browsers that do automatic "learned" identification of trackers do take time to identify what they consider trackers and start blocking them. e.g. that site says google analytics is not blocked by safari, yet I can look at Safari's tracker stats and see that it has identified and is blocking google analytics.

The header at media queries says “Fingerprinting resistance”. Some data point like screenwidth doesn’t immediately disclose you identity. But having a few data points helps with fingerprinting.

That said, my point stands that the bigger "reputable" trackers (e.g. the ones that exist on basically every website) are all blocked by the learned trackers techniques, and so should be listed as blocked on that site.

>By default, Privacy Badger receives periodic learning updates from Badger Sett, our Badger training project. This “remote learning” automatically discovers trackers present on thousands of the most popular sites on the Web. Privacy Badger no longer learns from your browsing by default, as “local learning” may make you more identifiable to websites. You may want to opt back in to local learning if you regularly browse less popular websites.

-- https://privacybadger.org/#How-does-Privacy-Badger-work

The full writeup:

https://www.eff.org/deeplinks/2020/10/privacy-badger-changin...

GPC does differ from Do Not Track in that the former is intended to carry the weight of law. See for example: https://cheq.ai/blog/what-is-a-global-privacy-control/

Regarding document.referrer, you are absolutely right that there is a cost/reward balance and most browsers have chosen to allow cross-site passing of the referrer. However, there are browsers on Android that do block cross-site referrer altogether (see https://privacytests.org/android.html).

"Media queries" refers to the fingerprinting threat where, for example, screen width and height is divulged. You are right that JavaScript can also be easily used to get screen width and height: any fingerprinting resistance feature should protect against screen fingerprinting via both JS and media queries, in my view. Some browsers already do that, as the results show.

Your question about scale is a good one. Some browsers (such as Firefox and Brave) embed fairly large blocklists. You are right that query parameters can be changed, but in practice I haven't seen any cases of that happening (yet).

As far as I am aware, Safari is (by default) blocking cookies/storage from Google Analytics and similar trackers, but not blocking the scripts themselves. You can see that cookie blocking reflected in the "Tracking cookie protection tests".

Anyway, "the Web" can work in a more user-friendly, less advertiser-friendly way, meaning the user has more control over what DNS lookups are made, what HTTP requests are sent and what remotely hosted code, e.g., Javascript, is run. I know this because I am using it in such a manner every day. There is nothing in the "technology" underlying the web that prevents it. The practices that necessitate something like "TCP", the Mozilla acronym not the IETF one, stem from (a) the widespread use of particular programs, e.g., popular web browsers that have user-hostile, advertising-friendly "features", and (b) web developer behaviour, e.g., stuffing web pages full of third party advertising-related links. They do not stem from the protocols ("technology") that comprises "the Web", e.g., RFC 1034 or RFC 2616.

Mozilla and other so-called "tech" companies portray "the Web" as something that is (a) only accessible through a narrow range of programs, namely a handful of popular browsers distributed by so-called "tech" companies, and (b) intricably tied to online advertising. Web developers, the majority of them now working for so-called "tech" companies, design websites that utilise "features" of these programs and similarly, based on their own self-interest, argue that this is "the Web". However this is only their preferred version of "the Web". This is the web as experienced using a particular handful of programs that put online advertising first and web users second.

However these so-called "tech" companies are not producing the majority of the web's content. Users are producing that content. The majority of it is not being directed (published) to the world. It is being directed to one other user or a small group of other users. The so-called "tech" companies are intermediaries that seek to promote a minority of users who desire to publish content for large audiences, as this is optimal for advertising purposes, Given the proliferation of these so-called "tech" companies as intermediaries that surveil people using the web in order to profit from selling advertising services, this presents an interesting technical challenge for the majority of web users. How can web users share content with each other using the Web without using so-called "tech" company website intermediaries that perform surveillance for advertising purposes.

The so-called "tech" companies, often including Mozilla, argue that online advertising is necessary for "the Web" to exist, and therefore so-called "tech" companies must exist to faciltate the advertising. But that argument feels disingenuous. For one, "the Web" existed before advertising was permitted on the network. Thus there is no technical limitation that requires advertising. Second, users are paying ISPs for their network connections to each other; they are not paying so-called "tech" companies. Thus, there is no financial limitation that requires advertising in order for the majority of users to share content with each other (cf. large audiences). Most web use is not publishing content to large audiences, it is sharing content with individuals or small groups. Thus most web users do not need a so-called "tech" company to help them publish content to the world.

So-called "tech" companies are only intermediaries, not content producers. They surveil web users for advertising puproses, a practice which they spin as "for the purpose of improving the Services". From the user's perspective "improving the Services" would mean reducing data collection, surveillance and the annoyance of advertising.

Silicon Valley and the so-called "tech" industry more generally have a blind spot for conflicts of interest.

My understanding is, it's a simplified explanation for a somewhat more complex policy.

The obvious thing - every site gets its own cookies - has always been the case: Those are first-party cookies.

The question is what happens when one site embeds content from a different site. Traditionally, there was no special behaviour for that case: If site A embeds an iframe from site B, the top-level document gets to see the cookies for A while the embedded document gets to see the cookies for site B. B's cookies here are 3rd-party cookies.

The problem is that the two documents can communicate, so if site B is embedded into many other sites, B and the other sites can cooperate to track the user across them using B's cookies as a sort of shared identifier. (Or more commonly, B will do the tracking and pay/otherwise incentivise the other sites to embed itself and pass the necessary information to the embedded document)

To avoid this, TCP introduces another level of partitioning: Cookies are not just partitioned by which site has access to it but also by the top-level site.

So site B now doesn't get a single cookie jar as before, it will get several jars "B, embedded by A", "B embedded by C", "B top-level" etc with separate sets of cookies. Hence it becomes impossible to pass a common identifier from one top-level site to another one and (this particular way of) cross-site tracking won't work anymore.

This is what software developers do, iterate to improve software.

So instead of having a million js snippets on your page, you have one google tag manager snippet and then your marketing team can inject 400mb of javascript into the site without bothering dev.

2) Marketing department has free reign (via Google Tag Manager) to add arbitrary javascript on any page with Google Tag Manager installed. Namely tracking scripts, adwords conversions, retargeting pixels, or really any arbitrary javascript without limitation.

Edit: Google Tag Manager can also be used to inject scripts that aren't inherently bad, like a 3rd party support/chat widget (Zendesk, Intercom, etc)

Blocking "googletagmanager.com" does break a few sites, but not enough that it matters.

[1] https://support.google.com/tagmanager/answer/6328489?hl=en

[2] https://www.akamai.com/blog/security/magecart-attack-disguis...

Disclaimer: I'm a FF user, not trying to say FF is bad, I just want to know how much of this is actually new cutting edge privacy protection vs. marketing fluff.

Will someonlineshop.com redirecting me to payments.mybank.com fail with Total Cookie Protection enabled because the payments site uses cookies to store the return url for the online shop ?

Your login cookie as far as the IdP is concerned lives on oauth.thirdparty.net and on a successful login the app issues you your own session token that lives on myapp.com.

This seems to be like a typical cat-and-mouse game. And browsers will not get more privacy friendly as long as there will be a trend that moves applications and basically every aspect of our lives into the browser thus making it unbelieveably complex.

I suspect that we will soon have to choose to either live as a "digital hermit" (links/neomutt and other lightweight apps that do only the one thing) or give up and join everyone with Youtube/Facebook/Twitter.

Also the upcoming WebGPU enabling by default in chrome will probably make it very simple to fingerprint almost anyone.