[whatwg] Private browsing vs. Storage and Databases

Aryeh Gregor Simetrical+w3c at gmail.com
Wed Apr 8 10:23:58 PDT 2009

On Wed, Apr 8, 2009 at 1:02 PM, Bil Corry <bil at corry.biz> wrote:
> Is there really a use case for wanting to show up at a site as yourself, but not have any footprint of the visit saved locally?

Yes.  The commonly-cited use-case is buying a present for your spouse:
you would like it to be a surprise, and therefore not show up in the
URL bar when they use the computer and type things.  The actual
use-case and basically the whole purpose of the feature, which people
tend to politely avoid mentioning, is viewing porn.

The feature is not intended to try hiding info about you from the
site.  It's not very useful for that.  If you don't want the site to
know about you, you'd want to delete info before the visit, and may as
well leave it alone after the visit.  Note that browsers do the exact
opposite: all delete info after the session, but only some hide info
from before the session.  You certainly wouldn't bother deleting
history or cached files, since the server doesn't know about those
anyway.  And you'd want to set privacy on a per-site basis, not a
per-session basis -- you say "I don't trust this site", not "I don't
trust any of the sites I'm going to visit in this particular browser
window until I close it (but I trust all other sites)".  The latter
would be bizarre.

The intent of private browsing mode is to say "I don't want other
people using this computer to know that this browser session ever
occurred".  You don't care if the site knows about you.  If that were
the use-case, the feature would be designed totally differently.

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