On Wed, Mar 18, 2026 at 8:32 AM Ken Buchanan <[email protected]> wrote:
> > > On Wed, Mar 18, 2026 at 10:16 AM Daniel Bratell <[email protected]> > wrote: > >> How obvious will the existence of browser stored credentials be to the >> web site? >> >> What if I clear site data in the browser? >> > > Since the credentials come from the passkey provider/password manager, > clearing site data has no effect. > In the TAG review, I thought everyone had agreed that if the user uses browser UI to sign out of a site (which is accomplished by clearing site data), the browser should hide the fact that the user has a passkey until the user next chooses to sign in with a passkey. I now see that you removed that section from the explainer after I last looked: https://github.com/w3c/webauthn/wiki/Explainer:-WebAuthn-immediate-mediation/_compare/cef140c78ffe6ea855eb3f8d3c56db7cb17596c8...874f2dcf4c3b831db8169a92ccf828a03ff6551e. At the very least, this should continue to live in the Alternatives Considered section, with the reason for choosing against it. But I'll re-iterate the TAG's <https://github.com/w3ctag/design-reviews/issues/1092#issuecomment-3630215411> feedback <https://github.com/w3ctag/design-reviews/issues/1092#issuecomment-3630215411> that it's user-hostile to force someone to go over to Incognito in order to hide the fact that they have an account. If I want to use the 'guest' flow on a site that I've previously logged into, the UI that you've mocked in the explainer <https://github.com/w3c/webauthn/wiki/Explainer:-WebAuthn-immediate-mediation#contextual-sign-in-moments> forces me to 'close' my attempt to check out in order to get to the guest flow. This seems likely to coerce users to sign in, since they don't actually want to 'close' their attempt to check out. Browsers shouldn't facilitate that. This touches on Alex's point about litigating specific UI choices: it's fine if there are some "good" UIs and some "bad" UIs for a proposed API shape. The problem with this one is that I haven't yet seen a UI design for it that gives the user a free choice between logging-in-with-their-passkey and using some other method to accomplish their goal. If no such UI exists, that's an issue with the API itself. Jeffrey In terms of obviousness, a site that wanted to know if UI was shown could > fairly easily determine it by timing how long it takes before the promise > is rejected (i.e., it can distinguish between no UI being shown, and UI > being shown but the user dismissing it). > > One limitation we've added is that in incognito mode this API behaves the > same as when there are no credentials available, based on users having a > higher expectation of privacy while using that mode. > > >> /Daniel >> On 2026-03-11 16:35, Ken Buchanan wrote: >> >> Hi Yoav, >> >> That's correct. Apple agrees with the use case but dislikes the >> information leakage. The website can easily infer that browser UI is being >> shown, which lets them know a passkey exists for this user even if the user >> does not choose to sign in with one. >> >> We spent some time exploring their alternative proposal. It ends up being >> something quite different, though, and we decided to continue with this >> based on partner feedback. Since in their case the promise would not be >> rejected if no passkeys are available, the website must offer an >> alternative on the page before the method is called. Much of the current >> design's value is that it allows the page to perform some action (such as a >> navigation) only if this API does not succeed. >> >> The two proposals can co-exist in the specification, and we haven't ruled >> out pursuing Apple's alternative also. They would be invoked in different >> situations. >> >> >> On Wed, Mar 11, 2026 at 11:21 AM Yoav Weiss (@Shopify) < >> [email protected]> wrote: >> >>> >>> >>> On Monday, March 9, 2026 at 7:51:08 PM UTC+1 Alex Russell wrote: >>> >>> Hey Ken, >>> >>> It's disappointing to hear that the TAG was trying to litigate specific >>> UI choices, rather than helping to guide the API's design. As a general >>> matter, we should not be specifying *any* explicit UI: >>> >>> https://infrequently.org/2020/07/why-ui-isnt-specified/ >>> >>> If we've made that mistake here, it's not too late to change course >>> (although it's reasonable to leave non-normative "for instance" examples >>> and Explainer illustrations). If we didn't, then I'm inclined to suggest >>> that we have a conversation with our friends on the TAG about the >>> opportunities for UI treatments that APIs provide vs. requirements. As I >>> understand your API, an explicit form treatment is still possible in any UI >>> that prefers that. Is that wrong? >>> >>> Best, >>> >>> Alex >>> >>> On Thursday, March 5, 2026 at 11:34:59 AM UTC-8 Ken Buchanan wrote: >>> >>> *Contact emails* >>> [email protected], [email protected] >>> >>> *Explainer* >>> https://github.com/w3c/webauthn/wiki/Explainer:-WebAuthn- >>> immediate-mediation >>> >>> *Specification* >>> https://github.com/w3c/webauthn/pull/2291 >>> >>> *Design docs* >>> >>> https://github.com/w3c/webauthn/wiki/Explainer:-WebAuthn- >>> immediate-mediation >>> >>> *Summary* >>> A new mode for navigator.credentials.get() that causes browser sign-in >>> UI to be displayed to the user if there is a passkey or password for the >>> site that is immediately known to the browser, or else rejects the promise >>> with NotAllowedError if there is no such credential available. This allows >>> the site to avoid showing a sign-in page if the browser can offer a choice >>> of sign-in credentials that are likely to succeed, while still allowing a >>> traditional sign-in page flow for cases where there are no such credentials. >>> >>> *Blink component* >>> Blink>WebAuthentication >>> <https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EWebAuthentication%22> >>> >>> *Web Feature ID* >>> webauthn <https://webstatus.dev/features/webauthn> >>> >>> *Motivation* >>> Most sign-in experiences on the web use sign-in pages that offer >>> multiple options for accessing an account, such as username/password input >>> fields, federated sign-in buttons, and sometimes explicit WebAuthn or >>> passkey buttons. When the browser is aware of passkeys or passwords that >>> the user has for the site, this API mode makes the sign-in page unnecessary >>> by instead showing simple browser account selection UI when the user begins >>> a sign-in attempt. Signing in with this flow reduces friction and avoids >>> user confusion from having to remember which sign-in option they have used >>> previously on a given site. The main difference between this and current >>> modal WebAuthn sign-in UI is that for users without any such credentials, >>> no browser UI will be shown, and their sign-in experience will be unchanged >>> from what it is today (typically, a navigation to the site's sign-in page). >>> >>> *Initial public proposal* >>> https://github.com/w3c/webauthn/issues/2228 >>> >>> *TAG review* >>> https://github.com/w3ctag/design-reviews/issues/1092 >>> >>> TAG has closed its review with unsatisfied on the basis that they do not >>> believe a modal browser dialog is preferable to a form for user sign-in >>> experiences. There was extensive discussion of this topic on both the TAG >>> review issue and the WebAuthn WG issue. >>> >>> This conflicts with the feedback we have received from developers of >>> major relying parties who believe this enables them to build meaningfully >>> better user experiences. They believe that a modal dialog that appears only >>> when passkeys are available will be more successful for users attempting to >>> sign in. Additionally, achieving the goal of signing in a user while >>> keeping them in the current page context is very difficult with the current >>> API. >>> >>> Apple has stated that it supports the goals of this mode, but has >>> objected on a different basis from TAG. It favors an alternative API form >>> that it believes will have better privacy properties ( >>> https://github.com/w3c/webauthn/issues/2228#issuecomment-3443764943). >>> Notably, >>> Apple's proposal and Immediate mode would be invoked in different >>> situations, and are not mutually exclusive. >>> >>> Since Immediate mode does not guarantee that UI will be shown on >>> invocation, we maintain flexibility to tweak this later in ways that limit >>> its use. >>> >>> *TAG review status* >>> Issues addressed >>> >>> *Origin Trial Name* >>> Immediate Mediation for Passkeys and Passwords >>> >>> *Chromium Trial Name* >>> WebAuthenticationImmediateGet >>> >>> *Origin Trial documentation link* >>> https://github.com/w3c/webauthn/wiki/Explainer:-WebAuthn- >>> immediate-mediation >>> >>> *WebFeature UseCounter name* >>> kCredentialsGetImmediateMediationWithWebAuthnAndPasswords >>> >>> *Risks* >>> >>> >>> *Interoperability and Compatibility* >>> *Gecko*: No signal (https://github.com/mozilla/standards-positions/issue >>> s/1239) >>> >>> *WebKit*: Negative (https://github.com/WebKit/standards-positions/issu >>> es/504) Feedback is on the WG issue: https://github.com/w3c/ >>> webauthn/issues/2228#issuecomment-3443764943 >>> >>> >>> Naively reading through WebKit folks' feedback, they seem supportive of >>> the use case, but interested in a different shape that won't expose the >>> presence of the passkey to the site. >>> Is there a chance to converge here? >>> >>> >>> >>> >>> *Web developers*: Positive (https://github.com/w >>> 3c/webauthn/issues/2228#issuecomment-3999513181) >>> >>> *Other signals*: >>> >>> *WebView application risks* >>> >>> Does this intent deprecate or change behavior of existing APIs, such >>> that it has potentially high risk for Android WebView-based applications? >>> *No information provided* >>> >>> >>> *Debuggability* >>> *No information provided* >>> >>> *Will this feature be supported on all six Blink platforms (Windows, >>> Mac, Linux, ChromeOS, Android, and Android WebView)?* >>> Yes >>> >>> *Is this feature fully tested by web-platform-tests >>> <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?* >>> Yes >>> https://wpt.fyi/results/webauthn/getcredential-ui-mode- >>> immediate.https.html?label=master&label=experimental& >>> aligned&q=getcredential-ui-mode-immediate.https.html >>> >>> *DevTrial instructions* >>> https://docs.google.com/document/d/18iV5eUBM4NVoNx0gqPSxPyJA >>> jPdrfIR75vcMDBewzZU/edit?tab=t.0#heading=h.uj0x12ysuohk >>> >>> *Flag name on about://flags* >>> web-authentication-immediate-get >>> >>> *Finch feature name* >>> WebAuthenticationImmediateGet >>> >>> *Rollout plan* >>> Will ship enabled for all users >>> >>> *Requires code in //chrome?* >>> True >>> >>> *Tracking bug* >>> https://issues.chromium.org/issues/408002783 >>> >>> *Launch bug* >>> https://launch.corp.google.com/launch/4394539 >>> >>> *Measurement* >>> Use counters: CredentialsGetImmediateMediationWithWebAuthnAndPasswords >>> CredentialsGetImmediateMediationWithWebAuthnOnly >>> CredentialsGetImmediateMediationWithPasswordsOnly We are also tracking >>> user interactions with the modal UI that will be shown when this is used. >>> >>> *Estimated milestones* >>> Shipping on desktop147Origin trial desktop first139Origin trial desktop >>> last141Origin trial extension 1 end milestone144DevTrial on >>> desktop136Shipping >>> on Android147DevTrial on Android142Shipping on WebView147 >>> >>> *Link to entry on the Chrome Platform Status* >>> https://chromestatus.com/feature/5164322780872704?gate=5177075746734080 >>> >>> *Links to previous Intent discussions* >>> Intent to Prototype: https://groups.google.com/a/chromium.org/d/msgid/ >>> blink-dev/CALjHGKrQEs4TDzuzb%3D0B00S4OmkE4a1NbZGi19sCueTKvN_ >>> m9w%40mail.gmail.com >>> Ready for Trial: https://groups.google.com/a/chromium.org/g/blink-dev/ >>> c/zC13ioLIZ_E/m/P-P6B6gNCQAJ >>> Intent to Experiment: https://groups.google.com/a/chromium.org/d/msgid >>> /blink-dev/CALjHGKpJkA9G6De6D4%3DRNSbLMRdy8Yfa6B%3DgDNWeqTyH >>> fv8sSg%40mail.gmail.com >>> Intent to Extend Experiment 1: https://groups.google.com/a >>> /chromium.org/d/msgid/blink-dev/CALjHGKpLbqYVnSMfNgxh45TSbP9 >>> j6AU2JvLWow%3DH1ihr5v%2Bj0A%40mail.gmail.com >>> >>> >>> This intent message was generated by Chrome Platform Status >>> <https://chromestatus.com/>. >>> >>> -- >> 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 [email protected]. >> To view this discussion visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CALjHGKoR0EskBNkLxcaRRO0wtfGe-0po0mxnFH_VhSnpFt49Zw%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CALjHGKoR0EskBNkLxcaRRO0wtfGe-0po0mxnFH_VhSnpFt49Zw%40mail.gmail.com?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 [email protected]. To view this discussion visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CANh-dX%3Dn_ahxsHV8qrkhrsxzLytvnTpTtX6JOtiWm24n9t1tZA%40mail.gmail.com.
