How to browse privately and avoid persistent tracking on a Mac, iPhone, and iPad


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.

Guest user account

In macOS, the best path of action is to log in as a guest user before using a Web browser. This special kind of account let someone hand their computer over to you (or vice versa) without needing providing any access to their own stuff. When you log in as guest, macOS creates a temporary account with its own settings. When the guest logs out, the entire account’s data get destroyed, which is an effective way to ensure privacy.

Visit the Users & Groups system preference pane, click the lock, enter credentials for an administrative account, and click Guest User in the list on the left. Then make sure Allow Guests to Log in to This Computer is checked.

privatei macos guestGlenn Fleishman

The Guest user in macOS lets you provide limited access to someone and deletes all associated data when that user logs out.

You can apply restrictions to the guest account by checking the box for Parental Controls, but only if FileVault is turned off. With FileVault full-disk encryption enabled, a guest user can only access Safari. (A bug in macOS lets you check the Enable Parental Controls box even with FileVault turned on.)

To get more access, the Mac’s owner could set up an account managed with Parental Controls. Parental Controls can be configured for another account from any administrative account via its preference pane. A managed account can be limited to running specific apps and either allowed to browse any website, barred from those deemed to be “adult,” or restricted to a limited set.

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