What Is Single Sign-On (SSO)?

If you’ve ever noticed you’re not asked for a password when opening a new work app — you just land straight in, or click one button and you’re through — that’s single sign-on, usually shortened to SSO.

Curious what’s actually checking your sign-in behind the scenes? See Azure AD vs On-Premises Active Directory.

What it means in practice

Instead of having a different password for email, file storage, your helpdesk system, and every other work app, you sign in once with your main company account. From then on, most other apps recognise that you’re already signed in and let you straight through, or show a quick “Sign in with Microsoft” (or similar) button that logs you in with one click — no separate password to remember or type.

Why it’s actually more secure, not less

It can feel like fewer passwords means less security, but it’s the opposite:

• One strong, well-protected account is far easier to defend than a dozen scattered ones — especially once it’s protected with multi-factor authentication (MFA) or a passkey.
• Fewer passwords floating around means fewer chances for one to be reused, written down, or caught up in a breach of some unrelated website.
• Access can be switched off instantly. When someone leaves the business, disabling their one main account immediately locks them out of everything connected to it, rather than IT having to track down and disable a password in every individual app.

What this looks like day to day

• Signing in once at the start of the day (usually on your laptop or via the Microsoft/Google sign-in screen) covers you for most other apps for the rest of the session.
• You may occasionally see a quick “Sign in with your organisation” screen the first time you open a new app — that’s SSO connecting the app to your main account, not a separate password to set up.
• If you’re prompted to re-enter your password partway through the day, that’s usually just your session timing out for security after a period of inactivity — sign in again as normal.

Caution

If you’re ever asked to sign in somewhere unexpected — a link in an email, a pop-up you weren’t expecting — stop and check the web address carefully before entering anything. SSO makes signing in feel seamless, which is exactly what a phishing page tries to imitate. See How to Spot and Report a Phishing Email if anything looks off.

If something goes wrong

• Stuck in a sign-in loop, or signed into the wrong account — sign out completely, close the browser, and sign in again with the correct account.
• An app says you’re not authorised, even though you’re signed in — this is usually a permissions issue on that specific app rather than your main account; contact support with the app name.
• Can’t sign in at all — contact support rather than repeatedly retrying, since several failed attempts can temporarily lock the account.