Contact emails abe...@chromium.org, victor...@chromium.org, jadekess...@chromium.org, miketa...@chromium.org
Explainer None Specification None Summary Before we proceed with User-Agent (UA) reduction, we want to allow sites that are not yet ready for the reduced UA string to get the full UA string, exposed in HTTP requests and in navigator.userAgent, navigator.appVersion, and navigator.platform, through a deprecation origin trial. Design Doc https://docs.google.com/document/d/1d-K43rzfDGxNM4H6Yzh5lV08KJwLsae06i4Q0A8snME Blink component Privacy>Fingerprinting <https://bugs.chromium.org/p/chromium/issues/list?q=component:Privacy%3EFingerprinting> TAG review https://github.com/w3ctag/design-reviews/issues/640 TAG review status TBD, but we have positive signals <https://github.com/w3ctag/design-reviews/issues/640#issuecomment-992698367> thus far. Risks Interoperability and Compatibility The compatibility risk is low, as we’re planning to send the full UA string in the deprecation origin trial, which is an existing behavior before UA reduction that sites already know how to parse. The deprecation origin trial is there simply to allow sites that aren’t yet prepared for the new behavior (the reduced UA string) to continue to receive the old behavior (the full UA string) for some time period. As for interoperability, the concern is again low because the deprecation origin trial is simply enabling previously-existing behavior to continue to operate for the sites that are enrolled. Experiment Summary The prerequisite of this trial is that developers know the deprecation origin trial is a temporary measure to allow more time to migrate off of the full UA string, and move to using User-Agent Client Hints (UA-CH) instead. By the end of the deprecation origin trial date, the Chrome browser will exclusively send the reduced UA string. The goal is to enable developers to ensure stability with our proposed changes. As for engaging with the trial itself, there will be two components controlled by the same origin trial: 1. Provide the full UA string in the associated Javascript APIs, if the deprecation origin trial is enabled. 2. A client hint that gets set when the deprecation origin trial is enabled, where the client hint indicates to the origin that the User-Agent request header contains the full user agent value. Because of the experimental nature of this client hint, a valid origin trial token must be sent in the response header by the origin for the client hint to take effect or be stored (in order to prevent platform burn-in for this temporary client hint). During the process of conducting the origin trial, we may find that we need to request an exception to the per-site (and possibly global) limits imposed by origin trials. In practice, origin trials rarely exceed their quota limits, but if necessary, there is time between when the limits have been exceeded and the origin trial is turned off, where we can work with the users on reducing their usage and/or lifting the limits. Please see the design document describing the experiment for more information. Experiment Goals The goal of this trial is to enable developers more time to migrate away from the full UA string and move towards adoption of UA-CH. Beginning in M101, we plan to send the reduced UA string in a phased rollout <https://blog.chromium.org/2021/09/user-agent-reduction-origin-trial-and-dates.html> approach. For those sites that haven’t been able to migrate their dependencies on the full UA string, the deprecation trial affords them more time to do so. We will be relying heavily on user and developer feedback to identify where breakage occurs. We request feedback to be provided in our GitHub repository https://github.com/abeyad/user-agent-reduction. When the deprecation origin trial is ready, we plan to publish developer guidance on how to enroll and provide feedback in the form of a blog post. Experiment Risks As the proposed changes are existing behavior, the experiment risks are low. Site breakage can take many forms, both obvious and non-obvious. However, since sites are in control of the Origin-Trial and Accept-CH headers, a site can quickly opt out of the experiment when breakage is encountered. Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/master/docs/testing/web_platform_tests.md> ? No. Flag name #full-user-agent Launch bug https://bugs.chromium.org/p/chromium/issues/detail?id=1232573 (for UA reduction) Tracking bug https://bugs.chromium.org/p/chromium/issues/detail?id=1282230 Link to entry on the Chrome Platform Status https://chromestatus.com/feature/5704553745874944 Links to previous Intent discussions I2E for UserAgentReduction: https://groups.google.com/a/chromium.org/g/blink-dev/c/R0xKm1B7qoQ/ -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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