[whatwg] Private browsing vs. Storage and Databases

[Aryeh Gregor]

On Tue, Apr 7, 2009 at 9:10 PM, Brady Eidson <beidson at apple.com> wrote:
> Caches are always assumed to be temporary and recoverable, and cookies have
> severe size and lifetime limitations placed on them (ie - the User Agent can
> never be excepted to keep cookies around for any predictable lifetime, per
> the cookies spec).
> LocalStorage and Databases are expected to be persistent unless a script or
> the user explicitly removes them.

Or unless the user just uses a different computer.  In Chrome's model,
at least, browsing a site in private-browsing mode is just the same as
using a public computer somewhere that you'll only use once and that
has no connection to the computer you normally use.  Surely you don't
expect apps to break or behave incorrectly when people use different
computers (possibly using some only once)?  That's a very common
use-case.

In other words, localStorage is *not* guaranteed to be persistent,
practically speaking.  The user might never use the computer again.