Sometimes you have no choice: your phone battery dies, you are travelling, the library computer is the only one available, or a colleague's PC is the quickest way to print a form. A public or shared computer is not your computer, and that changes the rules completely. It may remember your passwords, keep you logged in after you leave, record what you typed, or be running software you cannot see. None of that means you can never use one — it means you should use one with a plan. This guide gives you that plan: what to do before you sit down, what never to do while you are there, and the checklist to run before you walk away.
Why a Shared Computer Is Different from Your Own
On your own phone or laptop, you control the software, the updates and who touches it. On a shared computer, you control none of that. Other users have sat at the same keyboard before you, and others will sit there after you. Anything the computer saves — a login session, a downloaded file, a saved password, a browser history entry — is potentially available to the next person. Worse, a public computer could have keylogging software or a compromised browser installed by a previous user, and there is no reliable way for you to check from the outside. The safe assumption is simple: treat a public computer as a machine that remembers everything and belongs to strangers. Every habit below follows from that one assumption.
Before You Sit Down: Prepare on Your Own Device
The best public-computer security happens before you touch the keyboard. First, make sure your important accounts are protected by two-factor authentication — our 2FA guide walks through it. With 2FA on, even if someone recovers your password from a shared machine, they still cannot get in without your phone. Second, use unique passwords for every account (see our password security guide), so one exposed password does not unlock everything else. Third, if you know you will need a document, carry it on your own USB drive or download it from your own cloud account at the moment you need it, rather than emailing it to yourself on the shared machine and leaving copies behind.
Also decide in advance what you will NOT do on this machine. The list should include online banking, entering card details for a purchase, and changing important passwords. If a task involves money or your most sensitive accounts, wait until you are on your own device. A public computer is for reading, printing, filling forms and low-risk browsing — not for your financial life. Our safe online banking guide explains why banking deserves your own trusted device.
While You Work: The Rules That Matter Most
- Use private browsing. Open a private or incognito window (usually Ctrl+Shift+N or Ctrl+Shift+P). Private browsing does not make you anonymous and does not protect you from keyloggers, but it does stop the browser from saving your history, cookies and form data after you close the window. It is a real, useful layer — just not a complete shield, so never treat it as one.
- Never save passwords. When the browser asks "Save password?" or "Stay signed in?", always answer no. That prompt is the single most common way accounts get left behind on shared machines. If you accidentally click yes, delete the saved password before you leave (browser settings → passwords) and change that password from your own device later.
- Never let the browser remember card details. Decline every offer to save payment information, addresses and phone numbers. Autofill data left on a shared computer is a gift to the next user.
- Log in by typing the address yourself. Do not follow links from emails or messages to reach a login page on a shared machine — phishing pages are designed to look identical to real ones, and on an unfamiliar computer you cannot rely on saved bookmarks. Type the site address, check for HTTPS and the padlock, and read the domain character by character.
- Beware of shoulder surfing. In a library, office or internet café, someone behind you can read your screen or watch your fingers. Shield the keyboard when typing passwords, sit with your back to a wall where possible, and use your phone's screen to approve logins rather than typing codes where others can see them.
- Do not plug in unknown USB drives — and guard your own. A USB drive found lying around a public place can carry malware; never plug one into any computer, and never plug your own drive into a machine you do not trust without expecting that its contents could be copied. If you must transfer files, use your own cloud storage over an encrypted connection instead, and remove the files from the shared machine afterwards.
- Do not download software. Never install a "required" browser extension, viewer or app on a shared computer, no matter what a pop-up claims. Pop-ups demanding a download are a classic infection route, and installing software on someone else's machine is rarely legitimate anyway.
Files and Printing: Leave Nothing Behind
Every file you open or download on a shared computer is a file left behind unless you remove it. Download to one folder, work from it, and delete it — plus the browser's downloads list — before you leave. Empty the recycle bin or trash if you deleted files there, since deleted-but-not-emptied files are still recoverable. If you printed something, collect every page from the printer tray, including misprints and blank pages; a forgotten printout with personal details is one of the most common real-world leaks, and it needs no hacking at all.
Be careful with cloud storage on shared machines too. If you open your Google Drive or email to fetch a file, that session can persist after you close the tab unless you sign out properly. Always use the service's "Sign out" button rather than just closing the browser, and if the service offers "sign out of all devices" or a session list, check it from your own phone afterwards. Our cloud storage security guide covers session management in detail.
Before You Walk Away: The 2-Minute Checklist
- Signed out of every account (email, social media, cloud storage, shopping) — using each site's sign-out button, not just closing tabs
- Closed all private browsing windows
- Cleared browsing data for the session (history, cookies, cached files, downloads list) if you used a normal window at any point
- Deleted every file you downloaded or created, and emptied the trash
- Removed your USB drive (and checked you actually have it — drives left in ports are lost drives)
- Collected all printed pages from the printer tray
- Left no passwords saved — if the browser asked and you refused, you are fine; if you are unsure, check the browser's saved-password list
Two minutes, every time, without exception. Make it a ritual like locking your front door: you do not skip it because you are in a hurry.
Afterwards: What to Do from Your Own Device
Once you are back on your own phone or laptop, spend five minutes closing the loop. Check the recent-activity or session pages of the accounts you used (most email and social services show active sessions and let you revoke them) and sign out any session on the shared computer that might still be live. If you typed a password on a machine you now distrust — it looked tampered with, it behaved strangely, or you simply feel unsure — change that password from your own device, and change it everywhere you reused it. This is also the moment unique passwords pay off: changing one password is a small job; changing one password shared across ten accounts is a bad evening.
Watch for the warning signs in the following days: login alerts from unfamiliar locations, password-reset emails you did not request, or messages sent from your accounts that you did not write. If any appear, act immediately — change the password, revoke sessions, and check our hacked account recovery guide for the full recovery sequence.
Special Cases: Work, School and Hotel Computers
Work and school computers are shared in a different way: they are usually managed by an IT team, which is safer than a random public terminal but still not private. Assume your employer or institution can see activity on its machines, keep personal accounts and personal files off them, and never store personal passwords in a work browser. Hotel business-centre computers deserve the most caution of all — they are high-traffic, lightly maintained, and a known target for credential theft. On a hotel computer, stick to reading and printing, and do nothing that requires a password if you can possibly avoid it. Your phone, even on hotel WiFi with a VPN, is a safer choice for anything sensitive.
Key Takeaways
- Assume a shared computer remembers everything and belongs to strangers — every habit follows from that.
- Prepare in advance: 2FA on, unique passwords, and a clear list of things you will not do on the machine.
- Use private browsing, never save passwords or card details, type login addresses yourself, and guard against shoulder surfing.
- Leave nothing behind: sign out properly, delete downloads, empty the trash, collect printouts, take your USB drive.
- Afterwards, revoke stray sessions from your own device and change any password you now distrust.
- Every step here is defensive and legal — protecting your own accounts without ever touching anyone else's.