Contact emails
fla...@chromium.org, perryuw...@gmail.com

Specification
https://www.w3.org/TR/css-overscroll-1/#propdef-overscroll-behavior


Summary

The overscroll-behavior applies to all scroll container elements, regardless of 
whether those elements currently have overflowing content or are user 
scrollable. Developers can use overscroll-behavior to prevent scroll 
propagation on an `overflow: hidden` backdrop or an `overflow: auto` element 
without needing to consider whether it will currently be overflowing.



Blink component
Blink>Scroll


Web Feature ID
overscroll-behavior


TAG review
None


TAG review status
Not applicable


Risks




Interoperability and Compatibility

This should be implemented on other browsers as well, as it matches the 
specification. However, until this happens there are compatibility risks that 
some sites may over accidentally set overscroll-behavior on elements which 
don't currently apply today (either overflow: auto or not having overflow) and 
will start applying, or that developers will rely on this behavior and have 
accidental scroll chaining in other browsers until they implement it as well. 
This change will affect a large number of sites per 
https://chromestatus.com/metrics/feature/timeline/popularity/5596. I have done 
compat analysis of many of the top sites affected by this in 
https://issues.chromium.org/issues/41371072#comment45 and found it to either 
not have a meaningful impact or to better honor the developer specified intent.


Gecko: No signal

WebKit: No signal

Web developers: No signals

Other signals:


Ergonomics

This improves the ergonomics of overscroll-behavior, fixing the current 
unpredictable layout dependent behavior we have today.



Activation

It may be difficult for developers to take advantage of this fix before it is 
adopted in other browsers as it is likely not possible to feature detect. They 
could remove pre-existing hacks to get this functionality (ie ensuring 1px 
overflow) on supporting chromium browsers.



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




Debuggability

None



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?
Yes
https://wpt.fyi/results/css/css-overscroll-behavior/overscroll-behavior-without-overflow.html?label=experimental&label=master&aligned



Flag name on about://flags
None


Finch feature name
OverscrollBehaviorRespectedOnAllScrollContainers


Rollout plan
Will ship enabled for all users


Requires code in //chrome?
False


Measurement
The OverscrollBehaviorOnNonScrollableScrollContainer feature counter measures 
how often this new behavior is or would be triggered. 
https://chromestatus.com/metrics/feature/timeline/popularity/5596


Sample links

https://ebidel.github.io/demos/chatbox.html
https://codepen.io/rctneil/pen/rJYONj


Estimated milestones

No milestones specified



Anticipated spec changes

Open questions about a feature may be a source of future web compat or interop 
issues. Please list open issues (eg links to known github issues in the project 
for the feature specification) whose resolution may introduce web 
compat/interop risk (eg, changing to naming or structure of the API in a 
non-backward-compatible way).
None


Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5129635997941760?gate=5124735842910208


This intent message was generated by Chrome Platform Status.

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