Interactive diagnostic

Browser storage test

Verify that browser storage can write and read temporary values, then interpret quota and persistence without confusing them with disk capacity.

Processed locally in this browser

Reversible write test

Check whether web storage actually works

The test creates short values on the DeviceTriage origin and immediately removes them. It does not read or delete existing site data and does not request persistent-storage permission.

Only the measurement summary is kept in this browser for 7 days and added to Device Check and the JSON report. No raw frame, cookie value or site content is stored.

Four independent checksQuota is not total disk capacity

Test guide

What this test proves—and what it cannot

The browser storage test performs reversible first-party writes and reads, then reports the origin-level estimate and persistence state exposed by the Storage API. It separates blocked web storage from physical disk capacity without inspecting existing saved content.

Last reviewed: 2026-09-03

Signals measured

Whether temporary localStorage and sessionStorage values can be written and read
Whether a short first-party cookie can be set and removed
Estimated origin storage usage and quota when exposed
Whether this origin is already granted persistent storage

How the test works

Unique test keys are created, verified, and removed immediately.
The test cookie uses same-site first-party scope and is expired after reading.
Storage estimate and persistence are read-only calls; persistence is not requested.
Existing keys, cookies, offline files, and databases are not enumerated or cleared.

Interpreting the results

SignalWhat it meansNext step

All write checks workBasic first-party storage is available to DeviceTriage in this context.If one site fails, inspect that site's data, permissions, private mode, and implementation.

One storage type is unavailablePrivacy mode, browser policy, quota, disabled cookies, or an exception may block it.Compare normal mode and the affected site's permission before clearing data.

Low or missing quota estimateThe browser may restrict, round, or hide an estimate; it is not total free disk.Check operating-system free space separately if disk pressure is suspected.

Measurement limits

Quota is browser-managed, origin-specific, approximate, and can change without a hardware fault.
A passing small write does not guarantee that a large offline application can store every planned file.
Private mode and mobile operating systems can apply aggressive eviction policies.

Missing or privacy-reduced detail is not scored as a fault by itself.

Questions about this test

Will this test clear my browser data?

No. It removes only the uniquely named values and cookie it creates for the check. It does not enumerate or clear other site data.

Why is browser quota smaller than my disk?

Browsers allocate and report web storage under privacy, safety, free-space, and eviction rules. It is not a partition size or a disk-health reading.