Signed exchanges format:
Signed exchanges format: Implementation checkpoints (Chrome implements this):
Loading signed exchanges:
Signed HTTP Exchanges (or SXG) enables loading Web contents signed by the content publishers from anywhere, e.g. from a fast server, as if they came from the original publishers. Enabling this via Origin-Trials would allow SXGs to be hosted by the registrant sites without requiring users to manually turn on the flag.
Link to “Intent to Implement” blink-dev discussion
Goals for experimentation
To measure the real world impact of this feature before shipping. We will track the usage, error rates (especially for the SXG specific errors like certificate errors, validation errors and clock skews), stability and basic performance numbers.
We’d like to run this for one milestone to start with, starting with M71
(M71 cuts around Oct 11, will go Stable around beginning of Dec ~ end of Jan 2019)
Any risks when the experiment finishes?
We plan to have a separate sign-up for receiving the particular Accept header (i.e. Accept: “application/signed-exchange”) in incoming requests, and recommend that the interested sites also sign-up for the configuration. For the sites that don’t register this one won’t receive the Accept header, and even for the sites that registered Chrome will stop sending the Accept header once the experiment finishes. Therefore the sites can safely rely on the header not to return SXGs (that may not be processed by the UA, which would result in downloading the file). Also incompatible version of SXGs will still be redirected to its fallback URL (that is supposed to be consistent across format versions) therefore it shouldn’t harm user experiences.
Ongoing technical constraints
The status of SXG loading (including its error status) are shown on DevTools.
Will this feature be supported on all five Blink platforms supported by Origin Trials (Windows, Mac, Linux, Chrome OS, and Android)?
Link to entry on the feature dashboard
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LGTM to experiment, sounds very cool!
Possibly this is premature, but I wonder what the cross-browser testing strategy for this will be? Are the tests written for the implementation C++ unit tests, or something that could reasonably be shared?
LGTM to experiment, sounds very cool!Thanks!Possibly this is premature, but I wonder what the cross-browser testing strategy for this will be? Are the tests written for the implementation C++ unit tests, or something that could reasonably be shared?
Very good question! Yes currently we have bunch of unittests written in C++ for Chrome's implementation, but we are thinking about adding a set of .tentative WPT tests shortly. The initial set of tests would rely on a particular test-only UA configuration (i.e. UA would skip certificate errors) but we believe it'd be still useful for testing the basic loading behaviors.
To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/958e5734-a41a-43d5-bbaa-7cdfcaedd4ec%40chromium.org.
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