Intent to Ship: Out of order streaming

[Noam Rosenthal]

Contact emails
nrose...@chromium.org, foo...@chromium.org, barryp...@google.com

Explainer
https://github.com/WICG/declarative-partial-updates/blob/main/patching-explainer.md

Specification
https://github.com/whatwg/html/pull/11818

Summary
Use <template for> and processing instruction ranges (<?start> and
<?end>, or <?marker) to update existing parts of the document without
JS.

Blink component
Blink>HTML

Web Feature ID
No information provided

Motivation
Out of order streaming and partial updates are primitives that have
been part of userland libraries for about a decade.

Initial public proposal
https://github.com/WICG/declarative-partial-updates

TAG review
https://github.com/w3ctag/design-reviews/issues/1134

TAG review status
Issues addressed

Goals for experimentation
None

Risks


Interoperability and Compatibility
The main compat risk is re-introducing processing instructions, that
were parsed as comments up until now. This is mitigated by disallowing
HTML parsing of known processing instructions like <?xml-stylesheet?>,
and avoiding special characters like $. It was heavily tested against
the HTTP archive and ran in 50% Finch in beta. If new compat issues
arise we can special-case particular processing instruction targets
but it's likely not going to be necessary.

Gecko: Proposed support
(https://github.com/mozilla/standards-positions/issues/1369)

WebKit: Support (https://github.com/WebKit/standards-positions/issues/628)

Web developers: Positive
(https://github.com/wicG/declarative-partial-updates) See issues in
the WICG repo, lots of involvement from framework/CMS developers.
There were some mixed reviews on some threads (e.g.
https://news.ycombinator.com/item?id=48252957#48262499)

Other signals:

Enthusiasm (see the WICG repo) from frameworks and CMS like WordPress.
Drupal already has an open issue to support this
(https://www.drupal.org/project/drupal/issues/3590980)

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?

No


Debuggability
No information provided

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/html/dom/partial-updates/tentative?label=experimental&aligned

Flag name on about://flags
None

Finch feature name
DocumentPatching

Rollout plan
Will ship enabled for all users

Requires code in //chrome?
False

Tracking bug
https://issues.chromium.org/issues/431374376

Estimated milestones
Shipping on desktop150
DevTrial on desktop148
Shipping on Android150
DevTrial on Android148
Shipping on WebView150


Anticipated spec changes

Open questions about a feature may be a source of future web compat or
interop issues. Please list open issues (e.g. links to known github
issues in the project for the feature specification) whose resolution
may introduce web compat/interop risk (e.g., changing to naming or
structure of the API in a non-backward-compatible way).

There are a couple of small issues on the spec PR (e.g. how processing
instruction attributes are parsed) but they are converging and the
difference shouldn't be consequential.

Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5111042975465472?gate=5152413073539072

Links to previous Intent discussions
Intent to Prototype:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/6870fd9f.2b0a0220.2125de.0151.GAE%40google.com


This intent message was generated by Chrome Platform Status.

[Yoav Weiss (@Shopify)]

Thanks for tackling this important feature!

On Tuesday, May 26, 2026 at 4:17:50 PM UTC+2 Noam Rosenthal wrote:

Contact emails
nrose...@chromium.org, foo...@chromium.org, barryp...@google.com

Explainer
https://github.com/WICG/declarative-partial-updates/blob/main/patching-explainer.md

Specification
https://github.com/whatwg/html/pull/11818

What's preventing the PR from landing?

[Noam Rosenthal]

On Tue, May 26, 2026 at 3:44 PM Yoav Weiss (@Shopify)
<yoav...@chromium.org> wrote:
>
> Thanks for tackling this important feature!
>
> On Tuesday, May 26, 2026 at 4:17:50 PM UTC+2 Noam Rosenthal wrote:
>
> Contact emails
> nrose...@chromium.org, foo...@chromium.org, barryp...@google.com
>
> Explainer
> https://github.com/WICG/declarative-partial-updates/blob/main/patching-explainer.md
>
> Specification
> https://github.com/whatwg/html/pull/11818
>
>
> What's preventing the PR from landing?

We are working through some comments on the PR. None of pending issues
is about the API shape in a way that would create incompatibilities
and the current shape was discussed to minute details with Mozilla &
WebKit folks.
However this is a big PR (3 PRs to be precise) so it takes work to complete.
We are at WHATWG stage 3 (From whatwg site, stage 3: specification is
complete: all data structures, processing model, and API are fully
described. (It may still have small issues that will be identified by
editor review during this stage.)