Avoid persistent tracking on an iOS device
All browsers let you go incognito when you want to prevent leaving virtual footprints Glenn Fleishman shows how
Say you find yourself using the Web on a strange computer – maybe one owned by a relative or friend, or in a library or school. When using a computer or other device that you don’t control, you can enable a private-browsing mode to prevent leaving traces of your activities. That’s good for accidental security, as it keeps the next user of the device from visiting a site with your credentials, set in a cookie or via a login, when they didn’t
intend to. This an even better idea for shared computers where the subsequent user is someone you don’t know.
Likewise, you can set someone else up with private browsing on your Mac, so that they don’t have access to your settings (guest mode in Chrome) or can’t change your settings (all modes), although browsers don’t let you ‘lock’ a browser into that mode. You get better protection by setting up a different user account on a desktop Mac or using the guest account option described next.
Each browser’s privacy mode is a little different, so I’ll go through what kinds of data each destroys after a session and how to drop into the mode in each browser. As a general rule, while browsers in a private mode don’t keep a list of downloaded files, those files do persist on your drive after a browsing session is over.
Private browsing doesn’t precisely help with anonymity, or keeping your identity difficult to determine for a website on the other end or another party able to snoop your actions at some distant end point. It can, however, prevent sites from effectively depositing tracking cookies and other nasty elements, because when the private browsing session is over, everything associated that’s cached is supposed to be dumped.
Private Browsing in Safari for macOS and iOS
Apple isolates what it calls Private Browsing tabs from your regular browsing and from each other. Each tab can’t read information from other tabs. Apple doesn’t record autofill information entered or the pages you visit in a private browsing window. It prevents information leakage within the browser and through sync, too. It doesn’t pass pages through iCloud, so they don’t appear on other devices’
lists of open tabs, and Handoff doesn’t pass the open tab. Searches aren’t retained, and downloads in macOS aren’t shown in the Downloads list.
Safari for macOS also blocks reading browser cookies from your regular session and doesn’t store new ones after you close all private windows. Private browsing also blocks websites from using local storage options available via HTML5.
Apple’s detail about what happens in iOS is surprisingly thin. On its support site, the company notes, “Private
Browsing protects your private information and blocks some websites from tracking your search behaviour. Safari won’t remember the pages you visit, your search history, or your AutoFill information.” It would be nice for iOS details to have the same specificity as those provided for macOS, although in testing, they appear to be effectively the same.
In macOS, you create a Private Browsing window in Safari via File > New Private Window (Command-Shift-N). The new window and any subsequent private tabs you create have a dark background in the URL/search field at the top. Exiting private browser mode is a tab-by-tab operation; you can close an individual tab or a window full of private tabs.
In iOS, you tap the windows view button (which looks like two overlapping square) or, in some views, like iPhone landscape mode, you can pinch to get that view to appear. Tap the Private button, and it engages Private Browsing Mode. All tabs you open while in this mode are subject to the same privacy rules. Tap the Private button again to exit that browsing mode.
With iOS, you can’t merely exit the mode to destroy private browsing tabs. Instead, you have to bring up the windows view and close each tab one at a time. Otherwise, when you resume private browsing, the same tabs appear that you left open in your last private session.
Keep it secret, keep it partially safe
Using guest accounts and private browsing helps you prevent your surfing and your settings from commingling with others’ on computers or iPads you might use in passing, while also helping to ensure that someone else can’t scan back to see what you were up to later or access your accounts.