Chrome 138 will introduce a predictable storage quota from StorageManager's estimate API for sites that do not have unlimited storage permissions. It is possible to detect a user's browsing mode via the reported storage quota because the storage space made available is significantly smaller in incognito mode than in regular mode. This is a mitigation that prevents detection of a user's browsing mode via the storage API by reporting an artificial quota, equal to usage + min(10 GiB, disk rounded up to the nearest 1 GiB), in all browsing modes for sites with limited storage permissions. Sites with unlimited storage permissions will be unaffected. Enforced quota will also be unaffected.
This mitigates an avenue through which it is possible to detect that a user is in incognito mode.