Hi On Tuesday, April 26, 2022 at 9:31:37 PM UTC+3 abe...@google.com wrote:
> On Tue, Apr 26, 2022 at 4:14 AM Kirill Kandalov <kirill....@gmail.com> > wrote: > >> Hi, >> Thanks for the quick reply! >> >> On Monday, April 25, 2022 at 6:34:56 PM UTC+3 abe...@google.com wrote: >> >>> Hi Kirill, >>> >>> Thanks for your feedback. >>> >>> On Thu, Apr 21, 2022 at 2:16 PM Kirill Kandalov <kirill....@gmail.com> >>> wrote: >>> >>>> Hey all! >>>> >>>> Looks like I'm jumping on this train a little bit late, but still >>>> probably I’m not the last person on earth that is in the field of the web >>>> and only recently stumbled this change. After reading all this thread >>>> carefully I still feel that not everything was resolved so I’m posting it. >>>> >>>> Some of the reason that precise device detection is applied is to serve >>>> the best content for the users. Something that was mentioned in the thread >>>> previously. There’re multiple reasons for it that I see: >>>> 1. To provide the best UX based on the device – so mobile gets mobile >>>> web sites, desktop gets desktop experience and tablet is something in the >>>> gray zone – that’s where the use of the exact model is required, and based >>>> on device size, CPU capabilities and other properties the correct UI is >>>> provided. >>>> 2. Another requirement is to get full version of the browser and >>>> preferably the OS versions. As an example, if you work with video >>>> streaming, HLS, WebRTC and etc. they tend to break pretty often and could >>>> be fixed or broke again even between minor versions. And sometimes OS >>>> itself is a reason for it. So, the combination of these is required to >>>> allow/disallow some features and apply workarounds. >>>> 3. BI for detecting anomalies in specific version. You usually don’t >>>> need user’s fingerprint if the user is registered and logged in. But to be >>>> able to support the above 2 points and make other per device decisions the >>>> shortened UA is not enough. >>>> >>>> Experimenting lately with the UA-CH implementation for the websites, >>>> mostly the Critical-CH as high entropy CH are required to make the above >>>> decision on the “first hit”. The conclusion is that the proposed >>>> Critical-CH change is far from ideal, even harmful. The specs basically >>>> tell: >>>> 1. Browser sends a request to the server with a low entropy CH, e.g. >>>> “Sec-CH-UA-Mobile”. >>>> 2. Server sends in respond Critical-CH with list of high entropy CH, >>>> together with a full web page. >>>> 3. Browser detects new high entropy CH that are required and makes >>>> another request now with required CH >>>> 4. Server sends back a page that is adapted to the full UA-CH >>>> >>>> You all probably know the above, and some problems were raised already >>>> in this thread but I’ll mention them again as some weren’t answered: >>>> 1. Two requests – doubles the time till user receives the content – and >>>> there’re multiple researches that show how badly the load time affects the >>>> conversion. >>>> 2. The server renders the full page on first request and it’s being >>>> omitted: More time on meaningless respond sending, more traffic, more time >>>> on server creating the response – think of server going to DB – useless >>>> load on all layers. More power consumption… >>>> 3. How the server knows that the client will send a second request or >>>> not? Maybe the browser doesn’t support at all client hints then the server >>>> needs to prepare the whole page and not optimize internal BL. The other >>>> case is that browser supports CH but won’t send them anyway (if in the >>>> future user will opt out from some CH, if it will be available, or the >>>> privacy budget is empty). >>>> >>> >>> That's correct; if the browser doesn't support client hints, the >>> Critical-CH response header won't have any effect. There are also some >>> situations in which client hints won't get sent, for example: (1) insecure >>> request (e.g. not https), (2) the request is coming from a subresource or >>> embedded iframe and the top-level frame's permissions policy didn't >>> delegate, (3) Javascript is disabled, (4) UA string is overridden >>> >> So my point is that we need to know reliably in the first request on the >> server side if the second request is a possibility at all. >> > > I don't know if this is possible; the user agent could always send a > second request. > Exactly - we have no reliable way to know if the second request will be sent after the server replies. "User agent could always send a second request" - it's not always, there's some strict algorithm implemented in the browser. But server has no clue about it. That's why I say this should be improved in the spec. > > If a client would A. list supported client hints in the first request B. >> If the condition for second request are met (HTTPS, not iframe with invalid >> permission policy etc) only then the server would know how to respond >> correctly. >> >> > The main idea behind client hints is to turn the user agent information > into an active retrieval surface (the site has to explicitly request it). > So on the very first communication with that site, it's not possible for > the browser to know ahead of time. User agents could potentially create an > off-band registration mechanism that would seed a file that the browser > loads up, but management and update of that would be a big challenge and > not entirely reliable on its own. > And it means that client will pay for it in initial load time, and server will pay it in more computation. And I see no way this spec avoids it. Only the new, not production ready, proposals for the future. > > BTW if you raised the iframe topic. Is it enough for the page from the >> parent domain to set permission policy on the iframe without stating the >> target domain that this policy is given for? I'm seeing a very common >> scenario where parent domain A, embeds iframe with some Ad network from >> domain B, and when the page is rendered, the iframe, from domain B, >> redirects itself to the ad from domain C. That's how ad network works. And >> the site owner of domain A has no clue of domain C. >> > > The permissions policy does require specifying which origins the > permissions are applied to: > https://w3c.github.io/webappsec-permissions-policy/#examples > That's a big problem. Even huge. It's so big that I wanted to write all this sentence in capital letters. You basically wrote that any usage of ad network will be harmed by CH, in a non-resolvable way. As site owner A has no idea about banner/iframe from domain C that will be presented on his site. So everything served from C can only use low entropy CH. I'd say that it's a show stopper, unless some workaround could be proposed(!). How did ad-tech companies respond to this? > > >> >> >>>> 4. BL should be rewritten as now user makes sometimes 2 requests. >>>> >>> >>> That's correct in that Critical-CH will result in 2 network round >>> trips. There are two mitigations in place for this, with varying degrees >>> of availability: >>> >>> (1) Use the ACCEPT_CH frame in the ALPS extension, so that the requested >>> client hints are known at connection establishment time and thus, won't >>> require an extra round trip. This is currently only implemented in >>> BoringSSL (not yet in OpenSSL): >>> https://chromestatus.com/feature/5555544540577792 >>> >>> I read the spec, including >> https://datatracker.ietf.org/doc/html/draft-davidben-http-client-hint-reliability-02 >> It'll take time till web servers will support it (I didn't find any >> mention of IIS supporting this). Also the 3rd party LBs, like AWS ALB, >> don't share their work plan in this direction. So it's currently couldn't >> be used in production. >> > > Agree, it'll be a while before this gets large scale adoption. > > >> >> >>> (2) We recently launched a feature where the Accept-CH storage persists >>> beyond browser restarts, so hopefully the Critical-CH header should take >>> effect less (only the first navigation ever, as opposed to the first >>> navigation after the browser restarts or user session otherwise ends): >>> https://bugs.chromium.org/p/chromium/issues/detail?id=1296339. So >>> hopefully this should improve client hints coverage such that restarts via >>> Critical-CH are needed far less. >>> >> Unfortunately I get access denied on this topic. From your description it >> doesn't solve the first visit of the user, whose load time we need to >> optimize. Will the Accept-CH persists between different incognito visits to >> the same domain? If the answer is that it will not persist then it's also >> an use case that is not covered by the proposal. >> > > Sorry, the bug should be open to you now. Correct, the very first visit > by the user agent to that origin would require the extra round-trip if the > Critical-CH header is specified. > > >> >>> >> If you encounter any issues or have further feedback, please do file an >>> open issue at crbug.new using the Blink>Network>ClientHints component. >>> >> About CH in Chrome Dev Tools built-in device lists. They don't use CH at >> all, should I open it as a bug in the same tracker? It does allow to add >> custom devices based on CH. But I would expect that if CH is being promoted >> then the debugging tools would be ready for it too. Currently need to >> explain everyone how to manually add new devices and not to use the current >> list. >> > > Yes, please open any requests or bugs you find to the same component in > crbug. > > >> >>> >>>> The alternative solution that was discussed by developers is to use >>>> redirects that are sent from the server for more data. Basically, the >>>> scheme stays as the above but the server sends 307, or other redirect >>>> code, >>>> with Accept-CH, so after the redirect the client adds the missing CH. The >>>> discussed drawback was that there could be an infinite loop if it’s >>>> implemented wrongly. >>>> >>> Do you mean the 307 hits the same page in the redirect, but this time it >>> includes the client hints? That's effectively what the >>> CriticalClientHintsThrottle is doing now. And there are safeguards in >>> place in it to prevent infinite redirects: >>> https://source.chromium.org/chromium/chromium/src/+/main:content/browser/client_hints/critical_client_hints_throttle.cc;l=91-92 >>> >> Almost, with 307 response the browsers that don't support CH will do the >> redirect. It's different from 200 OK response with Critical-CH and empty >> body, in such case Chrome will do another request, and other browsers would >> be stuck with empty page. >> > > Are you saying that if the site sends Critical-CH and a 200 OK response, > browsers that don't support client hints would show an empty page? Why > wouldn't the browser just ignore the Critical-CH header if it doesn't > support client hints? I might not be following exactly.. > I was referring my previous example scenario. That's why it was hard to follow. I was talking about 2 options that server can reply, when the server also optimize the page render time. First option is to respond with 307 redirect, and the second is to send 200 ok with empty body - and rely solely on browser CH functionality that it will do the second request. In first case, current Chrome implementation also follows the redirect. Exactly like browsers that don't support CH.. In case of sending 200 ok with empty body, the drawback would be if we guessed incorrectly the potential second request of the browser then the user would stuck. I think the bottom line here is that the redirect that is being ignored or not ignored when Critical-CH sent, should be better described in the spec. So that there won't be different implementations of CH between different browsers. > >> >>> Benefits of this approach is that the server doesn’t waste time on full >>>> page render, the response size is lower and that the server is sure that >>>> the browser will make the second request. >>>> >>>> Tried to optimize the first approach, with Critical-CH, to save as much >>>> as possible on the first request, the response that was 200 with empty >>>> page >>>> (don’t do it on prod!). But it is not future proof. Where browser may not >>>> send second request at all. Also guessing that browser supports UA-CH is >>>> *not >>>> defined* – just heuristic that “Sec-CH-UA-Mobile” is set, and the >>>> second guess is that one of the high entropy is missing is by maintaining >>>> on server side list of all HE-CH and comparing it to the request. This >>>> list >>>> is also constantly changing so this is also a *not well-defined* part >>>> of the specification. >>>> >>>> Also tested the Critical-CH together with 307. So, even if the guess >>>> that browser doesn’t support CH is wrong, the browser will still follow >>>> the >>>> redirect and render the required page to the user. For browsers that >>>> support CH the expected behavior was to just make a second request and >>>> ignore the response. And here was a surprise, there was no second request >>>> to the page, the browser just followed the redirect. This behavior was >>>> mentioned only in the source code thread, and not in the specs: >>>> >>>> >>>> https://chromium.googlesource.com/chromium/src/+/refs/heads/main/components/client_hints/README.md >>>> >>>> <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fchromium.googlesource.com%2Fchromium%2Fsrc%2F%2B%2Frefs%2Fheads%2Fmain%2Fcomponents%2Fclient_hints%2FREADME.md&data=04%7C01%7Ckirillk%40top4.com%7C863c28c144d7423ac71c08da1e0a18a3%7C5add8cc5d607420c9cf4fc411e4cafd0%7C0%7C1%7C637855325982683054%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C2000&sdata=CyoyqpC0hFT51CldbM30WGosZRU8aZ3cb%2BhEBPNLN08%3D&reserved=0> >>>> >>>> *“The Critical-CH retry mechanism is implemented as >>>> content::CriticalClientHintsThrottle and all of the important logic is in >>>> WillProcessResponse. When a retry situation is found (and the redirected_ >>>> flag isn’t set) the header is stored, the new hints are stored as normal >>>> and the request is “restarted” (i.e. the response is changed to an >>>> internal >>>> redirect to the same location, which is also what DevTools sees).”* >>>> >>>> This message is already got long, and there’re more of non-answered >>>> questions about CH that deserve a separate post. But my main point is that >>>> there’s no defined way how to get the required high entropy client hints >>>> without harming the user and the web site owner. >>>> >>>> Regards >>>> On Friday, March 25, 2022 at 5:23:03 PM UTC+3 James Rosewell wrote: >>>> >>>>> Adding API Owners. >>>>> >>>>> I appreciate that you will be subject to internal controls and that it >>>>> may be taking some time for you to go through the required training and >>>>> compliance. Could you let this group know when that is completed please? >>>>> >>>>> We are now in a different world where blink-dev are part of the public >>>>> reporting and monitoring agreement entered into between Google and the >>>>> CMA. >>>>> We are keen to support your compliance efforts and are encouraging others >>>>> to understand the obligations you are now under. >>>>> >>>>> In relation to this specific proposal I’m concerned you made no >>>>> mention of the agreement or its status in relation to the commitments >>>>> when >>>>> you presented it last week at the W3C >>>>> <https://github.com/antifraudcg/meetings/issues/3> and show every >>>>> sign of progressing as if nothing has changed. >>>>> On Thursday, 24 March 2022 at 15:51:44 UTC mike...@chromium.org wrote: >>>>> >>>>>> Hi James, >>>>>> >>>>>> We are committed to achieving the purpose of the Privacy Sandbox >>>>>> commitments accepted by the CMA >>>>>> <https://blog.google/around-the-globe/google-europe/path-forward-privacy-sandbox/> >>>>>> >>>>>> in February 2022. We encourage feedback on how to better achieve that >>>>>> purpose through our technical proposals, and we will report publicly on >>>>>> feedback we receive as set out in the commitments. We are in constant >>>>>> dialogue with the CMA on these issues, and members of the web ecosystem >>>>>> are >>>>>> also welcome to discuss these issues with the CMA. We therefore hope >>>>>> that >>>>>> everyone will understand when we decline to participate in public >>>>>> discussions on legal or internal aspects of compliance with the >>>>>> commitments, or to detail our direct exchanges with the CMA. >>>>>> >>>>>> thanks, >>>>>> Mike >>>>>> >>>>>> On 3/17/22 10:53 AM, 'James Rosewell' via blink-dev wrote: >>>>>> >>>>>> Google and CMA reached an agreement on 4th February 2022 concerning >>>>>> Privacy Sandbox and Topics. The agreement requires Google to train >>>>>> staff in Annex 3 >>>>>> <https://assets.publishing.service.gov.uk/media/62052c6a8fa8f510a204374a/100222_Appendix_1A_Google_s_final_commitments.pdf>, >>>>>> >>>>>> and paragraph 4.119 >>>>>> <https://assets.publishing.service.gov.uk/media/62052c52e90e077f7881c975/Google_Sandbox_.pdf> >>>>>> >>>>>> states, *“Google has committed to instruct its staff and agents not >>>>>> to make claims to other market players that contradict the commitments, >>>>>> and >>>>>> to provide training to its relevant staff and agents to ensure that they >>>>>> are aware of the requirements of the Final Commitments”*. >>>>>> >>>>>> Paragraph 21 of the agreement states *“During the standstill period, >>>>>> the CMA may notify Google that competition law concerns remain such that >>>>>> the Purpose of the Commitments will not be achieved. Google will work >>>>>> with >>>>>> the CMA without delay to seek to resolve concerns raised and address >>>>>> comments made by the CMA with a view to achieving the Purpose of the >>>>>> Commitments. Google will inform the CMA of how it has responded to those >>>>>> comments”*. >>>>>> >>>>>> The standstill period is defined in the agreement as is User-Agent >>>>>> reduction. >>>>>> >>>>>> Will Google representatives confirm they have approval from the CMA >>>>>> to progress this proposal? If not then please can they confirm that the >>>>>> proposal is now delayed until such approval is provided? >>>>>> On Tuesday, 14 January 2020 at 11:22:00 UTC yo...@yoav.ws wrote: >>>>>> >>>>>>> Contact emails >>>>>>> >>>>>>> yoav...@chromium.org, aaro...@chromium.org >>>>>>> >>>>>>> Summary >>>>>>> >>>>>>> We want to freeze and unify (but not remove) the User Agent string >>>>>>> in HTTP requests as well as in `navigator.userAgent` >>>>>>> >>>>>>> Motivation >>>>>>> >>>>>>> The User-Agent string is an abundant source of passive >>>>>>> fingerprinting information about our users. It contains many details >>>>>>> about >>>>>>> the user’s browser and device as well as many lies ("Mozilla/5.0", >>>>>>> anyone?) >>>>>>> that were or are needed for compatibility purposes, as servers grew >>>>>>> reliant >>>>>>> on bad User Agent sniffing. >>>>>>> >>>>>>> On top of those privacy issues, User-Agent sniffing is an abundant >>>>>>> source of compatibility issues, in particular for minority browsers, >>>>>>> resulting in browsers lying about themselves (generally >>>>>>> <https://www.zdnet.com/article/vivaldi-to-change-user-agent-string-to-chrome-due-to-unfair-blocking/> >>>>>>> >>>>>>> or to specific sites >>>>>>> <https://github.com/mozilla/webcompat-addon/blob/master/src/injections/js/bug1472075-bankofamerica.com-ua-change.js>), >>>>>>> >>>>>>> and sites (including Google properties) being broken >>>>>>> <https://www.onmsft.com/news/google-has-apparently-blocked-its-stadia-cloud-gaming-service-on-the-chromium-based-microsoft-edge> >>>>>>> >>>>>>> in some browsers for no good reason. >>>>>>> >>>>>>> The above abuse makes it desirable to freeze the UA string and >>>>>>> replace it with a better mechanism. There have been past attempts at UA >>>>>>> string freezing from the Safari team, but without an alternative way to >>>>>>> perform UA based content-negotiation, they had to be partially reverted. >>>>>>> >>>>>>> >>>>>>> >>>>>>> The User Agent Client Hints >>>>>>> <https://wicg.github.io/ua-client-hints/> (UA-CH) feature provides >>>>>>> an alternate source for the information the User-Agent string provides, >>>>>>> both in its request header form as well as its JS API one. >>>>>>> >>>>>>> Its main advantages are: >>>>>>> >>>>>>> - >>>>>>> >>>>>>> It provides the required information only when the server >>>>>>> requests it, over secure connections, making any fingerprinting that >>>>>>> relies >>>>>>> on it be active fingerprinting, which enables such use to be >>>>>>> audited, as well as acted-upon by the browser (e.g. in a future >>>>>>> implementation of the Privacy Budget >>>>>>> <https://github.com/bslassey/privacy-budget>). >>>>>>> - >>>>>>> >>>>>>> It provides the information in small increments, so servers are >>>>>>> only exposed to the information they need and request, rather than >>>>>>> being >>>>>>> exposed to the full gamut of the UA string even if they are just >>>>>>> trying to >>>>>>> figure out one detail about the browser. (e.g. brand and major >>>>>>> version) >>>>>>> - >>>>>>> >>>>>>> Since it provides the information via dedicated fields, it >>>>>>> enables better ergonomics and makes it less likely for servers to >>>>>>> get it >>>>>>> wrong and cause compatibility issues. >>>>>>> - >>>>>>> >>>>>>> And finally, starting fresh will enable us to drop a lot of the >>>>>>> legacy baggage that the UA string carries (“Mozilla/5.0”, “like >>>>>>> Gecko”, >>>>>>> “like KHTML”, etc) going forward. >>>>>>> >>>>>>> >>>>>>> Once UA-CH ships >>>>>>> <https://groups.google.com/a/chromium.org/d/msg/blink-dev/A4wxFpvqUfA/g7iccl9ICgAJ> >>>>>>> >>>>>>> as an alternative means for browser-specific content adaptation, we >>>>>>> would >>>>>>> like to freeze the User-Agent string. >>>>>>> >>>>>>> We propose to deprecate at M81 (starting to emit console warnings in >>>>>>> pages that read that string in JS), freeze its version information at >>>>>>> M83, >>>>>>> and unify strings of different devices at M85. See detailed freezing >>>>>>> plan >>>>>>> below. >>>>>>> >>>>>>> This timeline provides 3 months for developers to move to the new >>>>>>> mechanism for their future browser and OS version needs, and 6 months >>>>>>> for >>>>>>> more sophisticated OS or device specific targeting. >>>>>>> >>>>>>> Freezing plan >>>>>>> >>>>>>> Different parts of the UA string have different compatibility >>>>>>> implications. >>>>>>> >>>>>>> Some parts of it, such as the browser version and the OS version, >>>>>>> can be frozen without any backwards compatibility implications. Values >>>>>>> that >>>>>>> worked in the past will continue to work in the future. >>>>>>> >>>>>>> Other parts, such as the model (for mobile devices) and the OS >>>>>>> platform, can have implications on sites that tailor their UI to the >>>>>>> underlying OS or that target a very specific model in their layout. >>>>>>> Such >>>>>>> sites will need to migrate to use UA-CH. >>>>>>> >>>>>>> As such we are planning to freeze the parts that are amenable to >>>>>>> freezing fairly early, and gradually unify the rest. >>>>>>> >>>>>>> >>>>>>> Milestone >>>>>>> >>>>>>> Stable date >>>>>>> >>>>>>> Action >>>>>>> >>>>>>> M81 >>>>>>> >>>>>>> Mid March ‘20 >>>>>>> >>>>>>> Deprecate access to `navigator.userAgent` >>>>>>> >>>>>>> M83 >>>>>>> >>>>>>> Early June ‘20 >>>>>>> >>>>>>> Freeze browser version and unify OS versions >>>>>>> >>>>>>> M85 >>>>>>> >>>>>>> Mid September ‘20 >>>>>>> >>>>>>> Unify desktop OS string as a common value for desktop browsers. >>>>>>> >>>>>>> Unify mobile OS/device strings as a similarly common value for those >>>>>>> at M85 (*) >>>>>>> >>>>>>> >>>>>>> (*) For the mobile value, we may split it further based on common >>>>>>> device dimensions, as a one-time exercise, to reduce the compatibility >>>>>>> risk >>>>>>> of unification. >>>>>>> >>>>>>> >>>>>>> >>>>>>> Interoperability and Compatibility Risk >>>>>>> >>>>>>> The compatibility risk varies at different stages. >>>>>>> >>>>>>> For the freezing planned for M83, the compatibility risk is low. >>>>>>> Existing UA sniffing code will continue to work as expected. It is only >>>>>>> future UA sniffing code that will need to change and use the UA client >>>>>>> hints instead. >>>>>>> >>>>>>> For the unification planned for M85, the compatibility risk is >>>>>>> medium. Some sites can modify their responses based on the OS and >>>>>>> device >>>>>>> model, and those sites will have to change their UA sniffing code to >>>>>>> use >>>>>>> UA-CH. We expect such sites to be well maintained (otherwise, how can >>>>>>> they >>>>>>> keep up with OS UI and device model changes?). Therefore, having 4 >>>>>>> releases >>>>>>> to modify their code seems sufficient. >>>>>>> >>>>>>> In the long term, we expect this change to improve compatibility, as >>>>>>> UA sniffing based on UA-CH is bound to be more reliable than the >>>>>>> current >>>>>>> status quo. >>>>>>> >>>>>>> As for interoperability, we have other vendors on board with UA >>>>>>> freezing, but not necessarily with the UA Client Hints mechanism, that >>>>>>> is >>>>>>> supposed to replace it. That can create a tricky situation, where >>>>>>> developers would need to rely on the User-Agent string for some >>>>>>> browsers >>>>>>> and on UA-CH for others. >>>>>>> >>>>>>> Edge: Public support >>>>>>> <https://twitter.com/_scottlow/status/1206831008261132289> >>>>>>> >>>>>>> Firefox: Public support >>>>>>> <https://github.com/mozilla/standards-positions/issues/202#issuecomment-558294095> >>>>>>> >>>>>>> for freezing the UA string - “freezing the User Agent string without >>>>>>> any >>>>>>> client hints—seems worth-prototyping” >>>>>>> >>>>>>> Safari: Shipped to some extent. Safari has attempted to completely >>>>>>> freeze <https://twitter.com/rmondello/status/943545865204989953> >>>>>>> the UA string in the past, without providing an alternative mechanism. >>>>>>> That >>>>>>> got a lot of pushback, which resulted in somewhat reverting that >>>>>>> decision. >>>>>>> Nowadays, their UA string seems frozen, other than updates to the OS >>>>>>> version and the browser major version. >>>>>>> >>>>>>> >>>>>>> Alternative implementation suggestion for web developers >>>>>>> >>>>>>> For many (most?) uses of UA sniffing today, a better tool for the >>>>>>> job would be to use feature detection. Where feature detection fails >>>>>>> developers, UA Client Hints >>>>>>> <https://wicg.github.io/ua-client-hints/> are the right path >>>>>>> forward. >>>>>>> >>>>>>> Potential deployment hurdles compared to status quo: >>>>>>> >>>>>>> - >>>>>>> >>>>>>> Third party services that rely on the UA string would need to >>>>>>> convince the sites that include them to delegate that information to >>>>>>> them >>>>>>> using Feature Policy. >>>>>>> - >>>>>>> >>>>>>> The opt-in based mechanism of Client Hints currently suffers >>>>>>> from the fact that on the very-first view, the browser have not yet >>>>>>> received the opt-in. That means that requiring specific UA >>>>>>> information >>>>>>> (e.g. device model, platform) on the very-first navigation request >>>>>>> may >>>>>>> incur a delay. We are exploring options to enable the opt-in to >>>>>>> happen >>>>>>> further down the stack to avoid that delay. >>>>>>> >>>>>>> >>>>>>> Usage information from UseCounter >>>>>>> <https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit/Source/core/page/UseCounter.h&sq=package:chromium&type=cs&q=file:UseCounter.h%20Feature&l=39> >>>>>>> >>>>>>> If we were going to remove the User-Agent string outright, the >>>>>>> answer to that would’ve been “a lot!!!!111”. >>>>>>> >>>>>>> Given that we are planning to freeze it, we expect the “removal” to >>>>>>> be mostly backwards compatible, barring cases of specific OS or device >>>>>>> adaptation. >>>>>>> >>>>>>> Client-side UA sniffing use counters >>>>>>> <https://www.chromestatus.com/metrics/feature/timeline/popularity/2663> >>>>>>> show it’s being used by ~90% of sites. But again, since we’re talking >>>>>>> about >>>>>>> freezing, it should not break most uses. >>>>>>> >>>>>>> Entry on the feature dashboard <https://www.chromestatus.com/> >>>>>>> >>>>>>> https://www.chromestatus.com/feature/5704553745874944 >>>>>>> >>>>>>> -- >>>>>> You received this message because you are subscribed to the Google >>>>>> Groups "blink-dev" group. >>>>>> To unsubscribe from this group and stop receiving emails from it, >>>>>> send an email to blink-dev+...@chromium.org. >>>>>> >>>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6e72d610-9978-4d7a-862a-5830edbf6b81n%40chromium.org >>>>>> >>>>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6e72d610-9978-4d7a-862a-5830edbf6b81n%40chromium.org?utm_medium=email&utm_source=footer> >>>>>> . >>>>>> >>>>>> >>>>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "blink-dev" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to blink-dev+...@chromium.org. >>>> >>> To view this discussion on the web visit >>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/575ebed2-697a-4169-84d4-5dce9a433fd7n%40chromium.org >>>> >>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/575ebed2-697a-4169-84d4-5dce9a433fd7n%40chromium.org?utm_medium=email&utm_source=footer> >>>> . >>>> >>> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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