One of the best things about passkeys is that they aren’t trapped on just one device. Even if you haven’t synced your passkeys through a cloud service like iCloud Keychain or Google Password Manager, you can still use your iPhone or Android phone as a “physical key” to sign into websites on any computer.
This cross-device login uses a combination of Bluetooth (to prove the phone is physically near the computer) and a QR code (to establish a secure encrypted connection).
If you aren’t already familiar with setting up and using passkeys, read this article first: A Beginner’s Guide to Passkeys: How to Set Them Up, Use Them, and Sync Across Devices
Here is how to use a passkey stored on your smartphone to sign into a website on your Windows PC or Mac.
Prerequisites
Before you start, ensure both your computer and your smartphone meet these requirements:
- Bluetooth is ON: Both devices must have Bluetooth enabled. They don’t need to be “paired,” but they need to be able to detect each other’s presence.
- A Passkey exists: You must have already created a passkey for that specific website and stored it on your phone (e.g., in your iPhone’s “Passwords” settings or Android’s “Google Password Manager”).
- Updated Browser: Use a modern browser like Chrome, Edge, or Safari.
Step-by-Step: Signing In
1. Initiate the Login on your Computer
Navigate to the website you want to access on your computer.
- Click the Sign In button.
- If the site recognizes your browser, it might automatically prompt you for a passkey.
- If it asks for a password instead, look for an option that says “Sign in with a passkey” or “Other ways to sign in.”
2. Choose “Use another device”
When the browser’s passkey window pops up, it may default to looking for a passkey stored on the computer (like Windows Hello or Touch ID). Since your passkey is on your phone, you need to redirect it:
- Select “Use another device”, “A mobile device”, or “iPhone, iPad, or Android device.”
- A QR code will then appear on your computer screen.
3. Scan the QR Code with your Phone
- Open the Camera app on your iPhone or Android.
- Point the camera at the QR code on your computer screen.
- Tap the yellow link or button that appears (it usually says something like “Sign in with a passkey”).
4. Authenticate on your Smartphone
Your phone will now ask you to prove it’s you.
- iPhone: You will be prompted to use Face ID or Touch ID.
- Android: You will be prompted to use your Fingerprint, Face Unlock, or Screen PIN.
- Once authenticated, your phone sends a secure “handshake” to your computer via Bluetooth.
5. Success
The website on your computer will automatically refresh and sign you in. You never had to type a single character of a password.
Troubleshooting Common Issues
| Issue | Solution |
| No QR code appears | Ensure your browser is up to date. If you’re on a corporate network, some security settings might block the cross-device handshake. |
| “Device not found” | Double-check that Bluetooth is enabled on both your phone and your computer. They must be within a few feet of each other. |
| Scan doesn’t work | Ensure you are using the native Camera app, not a third-party QR scanner, as the native apps are specifically designed to handle passkey requests. |
Why this is secure
Even though you are scanning a QR code, the actual “secret” (your private key) never leaves your phone. The computer and phone simply use Bluetooth to verify they are in the same room, preventing someone halfway across the world from trying to use your QR code to log into your account.
If you’re ready to simplify your online life and improve security, setting up passkeys is a smart move. Just make sure you’ve turned on device backups (like iCloud Passwords & Keychain or Google account sync), so you don’t lose access to your passkeys if a device is lost or replaced. Contact Computer Techs if you’d like help setting up passkeys to help secure your most important accounts.