Hey Patrick,
This sounds related to a previous experiment
(https://groups.google.com/a/chromium.org/g/blink-dev/c/9xWJK3IgJb4/m/SYLfUccOBgAJ)
- could you describe how this experiment is similar or different (or
perhaps builds upon the results from the previous experiment)?
thanks,
Mike
On 4/23/25 10:46 AM, Patrick Meenan wrote:
Contact emails
pmee...@chromium.org
Specification
None
Design docs
https://docs.google.com/document/d/1xaoF9iSOojrlPrHZaKIJMK4iRZKA3AD6pQvbSy4ueUQ/edit?usp=sharing
Summary
For a small number (hundreds) of hand-curated static third-party
scripts that are used on a large portion of the web, Chrome will use a
single-keyed HTTP cache to store those resources. This helps users and
site owners with faster performance for those scripts that are very
widely used while maintaining the privacy protections of the
partitioned disk cache. This feature targets the scripts that most
users are likely to see multiple times across multiple sites in any
given browsing session. They are usually not in the critical path of
the page loading and may not impact the common performance metrics but
they are still important for the healthy operation of the web. The
list of candidate scripts is curated from the HTTP Archive dataset.
This includes site-independent things like common analytics scripts,
social media embeds, video player embeds, captcha providers and ads
libraries. It allows for code that uses versioned URLs as long as the
versioning is not a manual process by embedders and that the same
version is sent to everybody at a given point in time with the same
contents. This does not include things like common Javascript
libraries where they are commonly self-hosted or where the URL
references a specific version of the library and it is up to site
owners to manually select a version.
Blink component
Blink>Network
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3ENetwork%22>
TAG review
None
TAG review status
Not applicable
Risks
Interoperability and Compatibility
This change is internal to Chrome and should be completely transparent
to the web platform with no interoperability risks.
/Gecko/: N/A
/WebKit/: N/A
/Web developers/: No signals
/Other signals/:
Ergonomics
N/A
Activation
N/A
Security
Cache partitioning added a level of privacy protection that is being
disabled for a small number of resources where it is deemed safe to do
so. The linked document and issue provide the details on the
protections that are in place to minimize the privacy exposure.
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?
None
Goals for experimentation
For the purposes of the experiment, we will target around a dozen of
the most-impactful scripts (mostly ads and analytics) and work with
the script owners to measure the resulting impact (on performance,
reliability and business metrics).
If these scripts show minimal impact from using a shared cache then
there is no value in the added complexity for the feature and it can
be documented and closed.
If there is significant impact then it is likely worth pursuing
further (and will also be documented for other similar efforts).
Ongoing technical constraints
None
Debuggability
The cache key used for any given resource is exposed in the netlog
<https://www.chromium.org/for-testers/providing-network-details/>
which can be used to verify if a given resource used the shared cache
or not.
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>?
No
Flag name on about://flags
None
Finch feature name
CacheSharingForPervasiveScripts
Non-finch justification
None
Requires code in //chrome?
False
Tracking bug
https://issues.chromium.org/u/1/issues/404196743
Measurement
The success of this feature will be measured directly with the owners
of a small number of targeted scripts with a web-exposed experiment.
Estimated milestones
No milestones specified
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5202380930678784
This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.
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