Lending the machine to someone for five minutes

Somebody needs to check a train time, print a document, or look something up because their own phone is flat. You hand the machine over. This card is about what becomes visible in those five minutes.

Almost nobody who borrows a laptop goes looking through it. That is the first thing to say, because the paranoid version of this card would be both unpleasant and wrong. The overwhelming majority of what a borrower sees is presented to them by the machine itself while they are trying to do the thing you lent it to them for.

The machine is helpful. That is its entire design goal. It completes what you started typing, it restores what you had open, it announces what has just arrived, and it offers your recent items first because that is usually what you want. Every one of those helpful behaviours is a small disclosure engine pointed at whoever is holding the device.

What they see

Whatever is already on screen is the obvious one, and it is also the one people handle correctly, because you can see it yourself before you hand the thing over. The interesting exposures are the ones that arrive afterwards.

• Autocomplete and suggestions. They type two letters into the address bar for a completely unrelated site and the browser proposes a list. Same with the search box, the file dialog, the messaging app. The suggestion list is a compressed history of what you do most, sorted by how much you do it.
• Notifications. A banner from a messaging app carrying the first line of a message, a mail preview, a delivery notification with a courier name and a status. These push themselves into view without anybody touching anything, and they arrive on their own schedule rather than yours.
• Open tabs and open windows. Alt-tabbing to find the browser reveals whatever else was running. A restored session reopens what was there last time. On a phone, the app switcher shows a small live picture of every recent app.
• Recent files and downloads. The downloads shelf, the recent documents list, the default folder a file dialog opens into. If someone is saving an attachment, the save dialog shows them the folder as it currently stands. See files you downloaded.
• The clipboard. One paste into a text box produces whatever was copied last, which on this subject is frequently an address. The clipboard card covers why that is a sharper exposure than it looks.

What they do not see

They do not see anything they did not look for and the machine did not offer. Nobody scrolls through a browser history for fun while checking a train time. Nobody opens a settings panel. Nobody goes into a folder they have no reason to open. The realistic exposure surface of a borrowed machine is the front page of every helpful feature, not the deep contents.

They also do not see the things that were never written down. A private browsing session that has been closed leaves nothing for autocomplete to offer, and the what lands on the disk card sets out which categories of trace survive a close and which do not. If a thing left no artifact, no amount of borrowing surfaces it.

And a borrower who does see something usually does not interpret it. An unfamiliar browser icon means nothing to most people. A string of characters in a clipboard means nothing without the context that makes it an address. Seeing is not the same as understanding, and the gap between them is wide for anyone who is not already familiar with the subject.

The five-minute case versus the overnight case

These are different situations and it helps to keep them apart. A machine handed over while you sit next to the person, for a defined task, with you watching the screen, exposes roughly what the screen shows plus whatever notification arrives during those minutes. That is a small and knowable set.

A machine lent for an evening, or handed to a family member who takes it into another room, is a different object. Time is the variable that matters, because the notification stream keeps running and the person relaxes into normal use. Nothing about the second case requires bad intent. It only requires enough minutes for the machine to keep being helpful.

What changes the answer

5 things change how much this action gives away. None of them takes it to zero, and none of them is a promise.

1. Look at the screen before it leaves your handsThe single cheapest thing here. Close what is open, check the tab bar, put the browser away rather than minimising it. This handles the entire category of exposure that people worry about most, and it handles none of the categories that arrive afterwards.
2. A second account or a guest sessionMost operating systems have a separate user account or guest mode with its own history, its own recent files and its own suggestions. Handing over that session instead of yours removes autocomplete, recent documents and the clipboard from the picture in one move. It does not stop notifications if they are configured system wide, and it is more friction than most lending situations will tolerate.
3. Turn off content in notification bannersEvery phone and most desktops can show that a message arrived without showing what it says or who it is from. This is a setting, not a habit, so it holds even when you forget. It does nothing about a notification you open yourself in front of somebody.
4. Stay in the roomBeing present while someone uses your machine is not surveillance of them, it is knowing what was on screen. It converts an unknown five minutes into a known five minutes, which is the difference between guessing and counting. It has no effect on a machine lent overnight.
5. Lend the task, not the deviceLooking the train time up yourself and reading it out solves the same problem with none of the exposure. This is often the honest answer and it costs nothing except a small amount of your time. It is not always available, and refusing to lend a machine you have lent a hundred times before is itself a noticeable act.

What this card is not

This card is not a claim that people who borrow your things are snooping. Nearly all of what it describes is accidental, produced by the device rather than the person.

Questions that come up

Does closing the browser before handing it over cover this?

It covers what is on screen and open, which is the largest single piece. It does not cover autocomplete suggestions, notification banners, the clipboard, or recent file lists, all of which are separate mechanisms with their own storage.

Is a phone safer to lend than a laptop?

Different rather than safer. A phone shows less at once, but the app switcher shows a picture of every recent app, notifications are more aggressive by default, and the messaging history is usually right there in the app someone was handed.