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:

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?

score 164 · Answer 1 · answered Mar 20 '12 at 10:27

164

Session Storage:

Local Storage:

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

answered Mar 20 '12 at 10:27

Talha

3

Thanks. Could you share the link to this reference? – Christophe Mar 20 '12 at 15:33
3

Link above is now Defunct this is another great resource: http://www.sitepoint.com/an-overview-of-the-web-storage-api/ – chrisjlee Dec 26 '13 at 20:21
The conclusion may be correct, but not the reasoning. Even if the storage were per-page, it could still persist across windows/tabs. – pyrocrasty Jul 18 '15 at 20:25

score 103 · Accepted Answer · edited May 26 '23 at 15:06

103

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.

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 '23 at 15:06

mltsy

answered Mar 16 '12 at 18:11

Rob W

Thanks! Would you have a reference to recommend, that explains localStorage in detail? – Christophe Mar 16 '12 at 18:27
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@Christophe [MDN: Storage](https://developer.mozilla.org/en/DOM/Storage) and [W3c: Web Storage](http://dev.w3.org/html5/webstorage/). – Rob W Mar 16 '12 at 18:30
1

well, even after reading the MDN page I still can't find the answer to my question... Anyway, thanks again! – Christophe Mar 16 '12 at 18:37
1

@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. – Rob W Mar 16 '12 at 18:44
1

Here's documentation of the `document.domain` API mentioned: https://html.spec.whatwg.org/multipage/browsers.html#relaxing-the-same-origin-restriction – mltsy Feb 10 '17 at 15:40
The [MDN: Web Storage API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Storage_API) doc does now specify: "sessionStorage maintains a separate storage area for each given origin [...]", where the "origin" is as defined here: [MDN: Origin](https://developer.mozilla.org/en-US/docs/Glossary/Origin) - i.e. sessionStorage and localStorage are partitioned by `scheme + hostname + port` – mltsy May 26 '23 at 15:03

2 Answers2