Two-step sign-in: which second step should you choose?

In brief

Two-step sign-in, also called two-factor authentication or 2FA, means a stolen password alone is not enough to get into your account. After the password, the service asks for a second proof: a code, a tap on your phone, or a physical key. Turning it on is the single most effective thing most people can do for their accounts. Which second step you choose matters less than having one, but the choice still makes a difference.

Text or email codes

A code is sent to your phone number or email address each time you sign in. It is the easiest to set up and far better than nothing. The weaknesses are that text messages can be intercepted or redirected if someone takes over your phone number, and that a scammer who already has your password can talk you into reading the code out. Use it when it is the only option, and never share a code with anyone who contacts you.

Authenticator apps

An app on your phone, such as Google Authenticator, Microsoft Authenticator or the one built into many password managers, generates a fresh six-digit code every thirty seconds. Nothing is sent over the network, so there is nothing to intercept. Set-up takes a minute per account: scan a QR code, type the first code to confirm. Save the backup codes the service gives you somewhere safe, because they are what get you in if you lose the phone.

Push approvals

Some services send a notification to your phone asking "Was this you?" and you tap to approve. This is convenient, but a stream of unexpected prompts is a sign that someone has your password and is hoping you will tap yes by accident. If you did not start the sign-in, tap no and change the password.

Security keys and passkeys

A security key is a small USB or NFC device you touch to approve a sign-in. A passkey does the same job using the phone or computer you already own. Both are tied to the real website's address, which means a fake site cannot use them at all. For your most important accounts, email above all, this is the strongest option available.

A simple rule for choosing

Use a passkey or security key wherever your email, bank and password manager offer one. Use an authenticator app for everything else that supports it. Leave text codes for services that offer nothing better. Whatever you choose, store the backup codes and keep your recovery phone number and email up to date, because recovery is where most people get stuck.

Sources and scope

This piece is ByteNib editorial analysis written for general readers. It reflects public guidance on multi-factor authentication from cybersecurity agencies, including the US Cybersecurity and Infrastructure Security Agency and the UK's National Cyber Security Centre, and the published account-security documentation of major platform providers. Product names are given as examples rather than recommendations.

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