HTML5 Local Storage

[Albareto McKenzie]

Hi Rob,

Html 5 look really promising and have a lot of cool features for developers, reading a bit about it I came across the Local Storage, I read that is is a much better way to store data than Cookies. I have a couple of questions about it, there they go:

How does the Storage store the information? I mean, is it a physical file in the system like Cookies were?
What does it make it better than Cookies?
Is it possible to delete this data? This question goes in both directions as developer and user, I mean, is it possible to programatically delete the data and as a user can I delete local data as I am able with individual cookies?

Thanks for coming here to help us out

Cheers

[Rob Crowther]

The main advantage local storage has over cookies is that the data doesn't get sent along with each HTTP request and response, saving you many bytes in network load and improving performance. How local storage is implemented depends on the browser, Firefox sticks them all into a SQLite database as far as I'm aware. As a user, a browser should provide an interface to clear stored data for any particular site. As a developer, there's a removeItem method.

[paul nisset]

Hi Rob,

I saw this response about local data in HTML5 and was kind of surprised at how it works.

Firefox sticks them all into a SQLite database as far as I'm aware.

This seems quite alarming in terms of performance .
Is is really quicker for a browser to open a database and run a query to access site specific data than to set and read a cookie ?

Thanks,
Paul

[Rob Crowther]

I doubt it, Firefox stores nearly everything in SQLite databases, including cookies I think. If filesytems were faster than databases, what would be the point of databases?

At this point I should make sure you're aware: I'm not an expert in writing browsers, or even filesystems vs databases, so someone could come along and point out I'm wrong any minute, but this is the impression I got from different defects I glanced through in Bugzilla over recent years. Mozilla have been pushing a lot of their stuff into SQLite instead of using custom storage solutions.

[Bear Bibeault]

Seems like an assumption without any basis in fact. Is there any evidence to support performance concerns with the use of SQLLite by Firefox?

[paul nisset]

I don't know how Firefox uses SqlLite . If it automatically opens up a database every time it starts, then writing to a database that is already in memory would be quicker than disk I/O.

[Rob Crowther]

Now that I'm no longer replying on my phone, here's a ls *.sqlite of my Firefox profile:

addons.sqlite
blanktab_abcd_test.sqlite
chromeappsstore.sqlite
content-prefs.sqlite
cookies.sqlite
downloads.sqlite
extensions.sqlite
formhistory.sqlite
permissions.sqlite
places.sqlite
search.sqlite
signons.sqlite
testpilot_earlyadopter_results.sqlite
urlclassifier3.sqlite
webappsstore.sqlite

Cookies are there on line 5, local storage data is in webappsstore.sqlite.

[Albareto McKenzie]

Thanks Rob for the replies and the others for adding info-discussion.

Cheers.