Web Storage: LocalStorage versus SessionStorage

Web Storage stores string keys and values in the browser per web origin. localStorage and sessionStorage are similar but have different lifetimes and scopes.

LocalStorage and SessionStorage

LocalStorage is available to pages of the same origin and usually remains after the browser closes. SessionStorage is also separated by tab and lasts for the page session. Private browsing and policy can restrict both.

How NetKarte checks it

Check LocalStorage and SessionStorage separately in NetKarte's Storage & privacy card. If only one is available, do not assume both work; examine settings affecting the storage area that failed.

NetKarte writes and immediately removes a temporary test key. It does not inspect existing data or storage from other sites. For a re-diagnosis, it temporarily stores the scroll position in SessionStorage and removes it after restoration.

Notes

“Available” does not guarantee capacity, retention time, or third-party access. Storage availability alone is not evidence that tracking is taking place.

Compare storage with cookies

Cookies are attached by the browser to matching HTTP requests. Web Storage is not automatically attached, but page scripts can read and send it; it is not inherently a communication-free safe store.

As an illustration, two same-site tabs normally access the same localStorage while sessionStorage belongs to each page session. Some ways of opening a tab copy initial session values, so matching values alone do not prove shared storage.

If unavailable

Check site permissions, capacity, and browsing mode. NetKarte writes and removes a small temporary key; it does not measure capacity. Run diagnostics again after changes. Availability proves neither tracking nor successful tracking prevention.