There is existing HTML syntax to delegate client hints to third-party content which requires client information lost by user agent reduction. Example: <meta name="accept-ch" value="sec-ch-dpr=(https://foo.bar https://baz.qux), sec-ch-width=(https://foo.bar)"> We shipped this syntax in M100 and got belated developer feedback that it’s confusing. We reached the conclusion it’s not too late to change course due to low adoption so far. This intent proposes a replacement syntax with the same feature set. Example: <meta http-equiv="delegate-ch" value="sec-ch-dpr https://foo.bar https://baz.qux; sec-ch-width https://foo.bar"> This proposal also removes the older syntax introduced in M100.
We’re switching from `name="accept-ch"` to `http-equiv="delegate-ch"` on advice that `http-equiv` should be used when the value is impacting the processing model. We’re switching from syntax close to HTTP Permissions-Policy to use syntax closer to the iframe allow attribute at the request of developers. Although this change is coming after a launch in M100, usage of the prior syntax is low (currently 0.000016%) and it seems worth taking the opportunity to reduce developer confusion and increase standards compliance.