Scope of sessionStorage and localStorage

Question

I read some documentation on sessionStorage and localStorage, but I don't understand what the scope is: the domain, a specific page?

For example, if I have the following pages:

http://example.com/products.aspx?productID=1

http://example.com/products.aspx?productID=2

http://example.com/services.aspx?serviceID=3

And if on each of the above pages I run (with idvalue being the value in the querystring):

localStorage.setItem('ID',idvalue);

Am I going to end up with 3 different values stored, or are the values going to overwrite each other?

David Klempfner · Accepted Answer · 2024-05-14 00:19:26Z

171

Session Storage:

Values persist only as long as the window or tab in which they are stored.
Values are only visible within the window or tab that created them.

Local Storage:

Values persist window and browser lifetimes.
Values are shared across every window or tab running at the same origin.

So, by reading and understanding this each key-value pair is unique for each domain, because local storage persist values across window or tab.

edited May 14, 2024 at 0:19

David Klempfner

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answered Mar 20, 2012 at 10:27

Talha

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3 Comments

Christophe Over a year ago

Thanks. Could you share the link to this reference?

chrisl-921fb74d Over a year ago

Link above is now Defunct this is another great resource: sitepoint.com/an-overview-of-the-web-storage-api

pyrocrasty Over a year ago

The conclusion may be correct, but not the reasoning. Even if the storage were per-page, it could still persist across windows/tabs.

mltsy · Accepted Answer · 2023-05-26 15:06:51Z

107

The values are going to overwrite each other. Each key-name pair is unique for a protocol and domain, regardless of the paths.

The affected domain can be changed via the document.domain property.

sub.example.com -> example.com is possible (subdomain)
sub.example.com -> other.example.com is not possible

References:

MDN: Web Storage API: "sessionStorage maintains a separate storage area for each given origin [...]"
MDN: Origin: "Two objects have the same origin only when the scheme, hostname, and port all match."

edited May 26, 2023 at 15:06

mltsy

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answered Mar 16, 2012 at 18:11

Rob W

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6 Comments

Christophe Over a year ago

Thanks! Would you have a reference to recommend, that explains localStorage in detail?

Rob W Over a year ago

@Christophe MDN: Storage and W3c: Web Storage.

Christophe Over a year ago

well, even after reading the MDN page I still can't find the answer to my question... Anyway, thanks again!

Rob W Over a year ago

@Christophe I have verified my statements a while back by viewing the sqlite(3) database called webappsstore.sqlite in my Firefox profile directory, using query SELECT scope FROM webappsstore2;. The result is the reverse of the domain, followed by the non-reversed protocol, and sufficed with the port, eg: gro.allizom.snodda.secivres.:https:443. As you can see, there's no mention of any path.

mltsy Over a year ago

Here's documentation of the document.domain API mentioned: html.spec.whatwg.org/multipage/…

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