Why Does Website Storage Differ from Disk?

A website can report a storage quota that is much smaller than the computer’s free disk space. This does not mean the disk was resized or that the profile has lost all remaining capacity. The page is reading an origin-specific browser estimate, while the operating system reports physical or logical disk availability.

Separate the website estimate from free disk space

Websites can call navigator.storage.estimate() to request two approximate values for the current origin:

• usage estimates how many bytes that site currently stores; and
• quota estimates how many bytes are available to that site or web application.

Neither value is a disk inventory. Browsers can account for compression, deduplication, and security-related obfuscation, so the returned numbers are not exact. The quota can also vary between origins. An HTTPS diagnostic page and the business site are different origins and should not be expected to report the same usage or quota.

Do not compare one site’s quota directly with the free-space number in the operating system. Also do not treat a rounded GiB label as proof of the exact number of bytes the site can write before browser storage policy intervenes.

Read the profile storage setting correctly

MaskPilot provides Storage available to websites in the profile’s fingerprint settings. The supported presets are 10 GiB, 20 GiB, and 50 GiB, with 20 GiB selected by default for a new profile.

The saved preset is supplied when the next browser process starts. It does not reserve that amount of physical disk space, create site data, clear existing IndexedDB records, or grant a site permission to store unlimited data. Browser policy and the current origin’s existing usage still belong to the storage workflow.

Choose a stable preset for the intended environment rather than changing it until one checker displays the computer’s free-disk value.

Verify the saved preset after a full restart

1. In the affected profile, record the page address, browser version, reported usage, reported quota, and test time.
2. Confirm that the page uses HTTPS and that you are comparing the same origin on every run.
3. Fully close the profile and wait until its status becomes available.
4. Edit the same profile and locate Storage available to websites in the fingerprint settings.
5. If a correction is necessary, select one supported preset and save without changing unrelated fingerprint or proxy fields.
6. Relaunch the same profile, return to the same origin, and repeat the measurement once without another edit.

Fingerprint settings are loaded when the browser process starts. If the old result remains after a complete relaunch, follow why profile settings did not apply before changing another field.

Test capacity without mixing it with site data

Quota and usage answer different questions. Writing data can raise usage, while clearing one database may not remove every byte attributed to that origin immediately. A single before-and-after difference is therefore not a reliable fingerprint diagnosis by itself.

Use a test profile and non-sensitive test origin when validating large writes. Do not fill a production profile’s storage merely to reach a limit. If the real workflow fails, capture the browser error, requested write size, current origin, and remaining physical disk space. That evidence distinguishes a site storage failure from a profile-setting mismatch.

Browser storage is also different from login persistence. If the problem is that a website asks you to sign in again, use the login-state troubleshooting steps instead of increasing the quota first.

Know when to investigate further

No correction is normally required when the same profile returns a stable estimate for the same origin and the only disagreement is with the operating system’s free-space display. Those values describe different boundaries.

Investigate further when the result changes across full restarts without a profile edit, when the selected preset was not applied, or when the site reports a real write failure. Change one variable at a time and keep the browser version, origin, and profile constant. For the wider settings lifecycle, see configure a stable browser fingerprint.

MDN documents that StorageManager.estimate() returns approximate, origin-specific usage and quota values. Its Storage API guide explains browser storage buckets, persistence, quotas, and eviction behavior.