Intent to Experiment: IncognitoStaticStorageQuota

[Chromestatus]

Contact emails

michalh...@google.com, b...@google.com

Explainer

https://github.com/explainers-by-googlers/static-storage-quota

Specification

No information provided

Summary

Fixes a bug in the predictable-storage-quota that allows Incognito mode to be detected. A change introduced recently to Stable, buckets the result of the StorageManager's estimate API for sites that do not have unlimited storage permission to max(10Gib, ceil(actual_quota_in_Gib)) + usage. However, in incognito mode, the actual quota value is based on a fraction of available RAM, instead of the disk space - providing an Incognito detection surface. This change fixes the value of this API for Incognito Mode to the maximal bucket of: usage + 10Gib. Discussion on the original feature available here: https://groups.google.com/a/chromium.org/g/blink-dev/c/7q0YGQNVkjs/m/mpYkQVWpAQAJ This is a new Chromestatus in place of an original PSA, as this launch should start with an I2E to ensure the breakage risk is properly addressed. See https://groups.google.com/a/chromium.org/g/blink-dev/c/00aHBCiUGzo/m/B0Dq06SFAQAJ.

Blink component

Blink>Storage>Quota

Web Feature ID

storage-manager

Search tags

incognito, quota, storage

TAG review

No information provided

TAG review status

Pending

Goals for experimentation

None

Risks

Interoperability and Compatibility

No information provided

Gecko: No signal

WebKit: No signal

Web developers: No signals

Other signals:

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 information provided

Ongoing technical constraints

No information provided

Debuggability

No information provided

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, ChromeOS, Android, and Android WebView)?

No

Is this feature fully tested by web-platform-tests?

No

Flag name on about://flags

No information provided

Finch feature name

kIncognitoStaticStorageQuota

Requires code in //chrome?

False

Tracking bug

https://issues.chromium.org/issues/464484739

Estimated milestones

No milestones specified

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5117411264167936?gate=5943068999155712

This intent message was generated by Chrome Platform Status.

[Dan Clark]

Can you clarify the planned timeline for the experiment? Is my understanding correct that the idea is to roll this out via finch, rather than asking people to opt-in to an Origin Trial?

-- Dan

[Michał Hoffmann]

The planned timeline is a usual finch deployment with a full release in M151. The experiment for 50% of Canary+Dev+Beta is already up and running for some time with no breakages detected.

I was asked for an explicit I2E (a thread mentioned in the summary) before experimenting on stable. The usual rollout is planned, however since the change is Incognito only I wonder if starting with more than 1% of stable would reveal more about the possible effects of the feature. If so - I assume I'd need more approvals from owners there. 

Let me know what's the best approach for you
Michał

[Mike Taylor]

Thanks Michal - but I'm a little confused. 

Dan is asking which milestones you would like to run a 1% experiment on (or if you're planning to run an Origin Trial - and it looks like you aren't) to flush out any compat issues. Are you saying you would like to launch in M151, or start the 1% experiment in 151? If the former, for how many milestones (this is Dan's question)?

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[Michał Hoffmann]

Sorry for the confusion! To clarify:

- The experimenting on Stable could start right away - so a week after 100% stable release of M150 according to the best Finch practices.

- Once we have reliable data on 1% - so a week or two into the experimentation, I want to boost it to 10% of stable, as it's hard to investigate incognito effects on low traffic. The 10% experiment would run for another 2 weeks of data unless any concerns arise.

- The full release will be in M151, after both stages of an experiment, provided no negative signals on compat. 

Does that answer your question?

[Alex Russell]

Hey Michal,

We discussed this morning at API OWNERS and appreciate you bringing this to us. From a compat perspective, the Finch'd rollout plan sounds good, and we wish you luck.

From a Blink process perspective, we think this is more of an Intent-to-Ship, and are agreeing to treat it as such. With that caveat, and with the Finch rollout plan in play, LGTM1.

[Yoav Weiss (@Shopify)]

LGTM2

[Mike Taylor]

On 6/24/26 11:22 a.m., Alex Russell wrote:

Hey Michal,

We discussed this morning at API OWNERS and appreciate you bringing this to us. From a compat perspective, the Finch'd rollout plan sounds good, and we wish you luck.

From a Blink process perspective, we think this is more of an Intent-to-Ship, and are agreeing to treat it as such. With that caveat, and with the Finch rollout plan in play, LGTM1.

LGTM2 - thanks for the careful rollout plan. Good luck!

[Mike Taylor]

(or LGTM3)