Could you please request Debuggability and Testing bits in your
chromestatus entry?
On 11/8/25 4:32 a.m., Cammie Smith Barnes wrote:
Intent to deprecate and remove Shared Storage
Contact emails
[email protected]
Explainer
https://github.com/WICG/shared-storage/blob/main/README.md
<https://github.com/WICG/shared-storage/blob/main/README.md>
Specification
https://wicg.github.io/shared-storage/
<https://wicg.github.io/shared-storage/>
Summary
The Shared Storage API is a privacy-preserving web API to enable
storage that is not partitioned by first-party site.
Following Chrome's announcement
<https://privacysandbox.com/news/privacy-sandbox-next-steps/>that the
current approach to third-party cookies will be maintained, we are now
planning to deprecate and remove the Shared Storage API (along with
certain other Privacy Sandbox APIs, as outlined on the Privacy Sandbox
feature status page <https://privacysandbox.google.com/overview/status>).
Interest in the Shared Storage API has decreased since the
announcement. Use of sharedStorage.worklet.addModule()
<https://chromestatus.com/metrics/feature/timeline/popularity/4264>has
decreased ~20% from its peak of 7.35% of page loads down to 5.85% of
page loads. Use of sharedStorage.createWorklet()
<https://chromestatus.com/metrics/feature/timeline/popularity/4836>has
decreased ~82% from 4.87% to 0.864% of page loads. Use of
sharedStorage.run()
<https://chromestatus.com/metrics/feature/timeline/popularity/4270>has
decreased ~30% from 5.28% to 3.71% of page loads. Use of
sharedStorage.selectURL()
<https://chromestatus.com/metrics/feature/timeline/popularity/4269>has
decreased ~28% from 6.24% to 4.51% of page loads. Use of sharedStorage
overall
<https://chromestatus.com/metrics/feature/timeline/popularity/4263>has
decreased ~9% from 11.91% of page loads to 10.86% of page loads.
Blink component
Blink>Storage>SharedStorage
<https://issues.chromium.org/issues?q=customfield1222907:%22Blink%3EStorage%3ESharedStorage%22>
Web Feature ID
None
Motivation
Chrome has announced
<https://privacysandbox.com/news/update-on-plans-for-privacy-sandbox-technologies/>that
the current approach to third-party cookies will be maintained. Given
this, we expect adoption to decrease over time (currently at ~11%
<https://chromestatus.com/metrics/feature/timeline/popularity/4263>of
page loads) as the main use cases for Shared Storage will remain
possible in Chrome using third-party cookies. Further, other browser
engines have not signaled interest in launching the API. See also the
initial public proposal below.
Developer-facing impact
Sites that are using the Shared Storage API that do not migrate to
alternative solutions may experience a disruption in functionality,
and in particular all writes, reads, and worklet operations will fail.
If continued usage numbers warrant, we will take steps to minimize any
risk of actual page breakage, e.g. by temporarily retaining stub
implementations of the window-exposed methods that are still being
called most frequently.
The following API surfaces will be removed:
*
All of the Shared Storage JavaScript functions exposed to the
Window
<https://github.com/WICG/shared-storage/blob/main/README.md#outside-of-worklets-eg-places-where-writing-can-happen>will
be removed or replaced with stub implementations:
o
`window.sharedStorage.worklet.addModule()`
o
`window.sharedStorage.createWorklet()`
o
`window.sharedStorage.worklet.run()`/`sharedStorage.run()`
o
`window.sharedStorage.worklet.selectURL()`/`sharedStorage.selectURL()`
o
`window.sharedStorage.set()`
o
`window.sharedStorage.append()`
o
`window.sharedStorage.delete()`
o
`window.sharedStorage.clear()`
o
`window.sharedStorage.batchUpdate()`
*
All of the Shared Storage JavaScript functions exposed only to the
SharedStorageWorklet
<https://github.com/WICG/shared-storage/blob/main/README.md#in-the-worklet-during-an-operation>will
be removed. Since the worklet operation methods
(`sharedStorage.run()` and `sharedStorage.selectURL()` listed
above) will be removed or replaced with no-op stub
implementations, there will be no calls to any
SharedStorageWorklet-exposed Shared Storage JavaScript functions,
and so removing them will cause no breakage.
*
The SharedStorageWorklet interface will be removed or replaced by
a stub worklet interface (potentially for `addModule`, `run`,
`selectURL` stub implementations).
*
Consequently the `sharedStorage.worklet` attribute will either be
removed or updated to the stub worklet interface type pending removal.
*
The `sharedStorage.context` attribute will be removed, along with
the related `setSharedStorageContext()` method on fenced frame
configs. We will measure the usage of `setSharedStorageContext()`
to determine whether it should be replaced with a no-op stub
implementation instead.
*
The `sharedstoragewritable` attribute on <iframe> and <img>
elements will be ignored.
*
The `sharedStorageWritable` option in the fetch() API's
RequestInit will be a no-op.
*
Consequently, the `Sec-Shared-Storage-Writable` and
`Sec-Shared-Storage-Data-Origin` request headers will no longer be
sent, and the `Shared-Storage-Write` and
`Shared-Storage-Cross-Origin-Worklet-Allowed` response headers
will no longer be honored.
*
The “shared-storage” and “shared-storage-select-url” permissions
policy-controlled features will be removed along with the APIs.
Since the APIs they control will no longer exist, the permission
policies will have no effect and their removal is not considered a
breaking change.
*
The `sharedStorage` attribute on the Window will be removed once
all stub implementations are no longer needed and are removed.
Estimated milestones
Planning to deprecate in M144 and remove in M150.
Currently, ~11%
<https://chromestatus.com/metrics/feature/timeline/popularity/4263>of
page loads use Shared Storage API. While this usage is quite high for
a deprecation and removal, it is driven by a small number of
third-party ad tech scripts present on a large number of sites. We
will continue to monitor usage in addition to providing comprehensive
updates on privacysandbox.google.com
<https://privacysandbox.google.com/>with the status of the API and
deprecation plans <https://privacysandbox.google.com/overview/status>.
We will proactively work toward reducing usage to low levels once this
intent is approved, including disallowing any new enrollment sign-ups,
and contacting enrolled sites to inform them about the deprecation
timelines.
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5076349064708096
<https://chromestatus.com/feature/5076349064708096>
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