Should Yubico Security Key appear in Finder on MacBook Air?

No — when you plug a Yubico Security Key into your Mac, it will not appear in Finder like a USB flash drive. That’s because YubiKeys don’t act as storage devices. Instead, they present themselves as a security/authentication device using interfaces like HID (keyboard), CCID (smart card), or FIDO. Finder only shows devices that expose a filesystem, which a YubiKey intentionally does not.

To confirm your key is recognized, check System Settings → Privacy & Security → Security Keys, or open System Information → USB and look for it there. You’ll also see it light up or respond when a website or app prompts for security-key authentication.

Alternately, you can use the Yubico Manager app.

Ok, there is no real security key setup ... other than adding passkeys to it so that you can use it to access secured websites.

The following are the steps I followed to initially set up my Yubikeys:

1. Insert the security key it into one of your Mac’s USB ports (or use NFC if your model supports it). macOS doesn’t need drivers. (For reference, I have two types of keys: A YubiKey 5 NFC which has a USB-A connector, and a YubiKey 5C NFC which has a USB-C connector.)
2. Download and install YubiKey Manager from Yubico’s site. This lets you view and configure features like FIDO2, OTP, and PIV. Note: The most common feature is FIDO2.
3. Open YubiKey Manager and confirm the key shows up. This ensures the hardware and macOS are communicating correctly.
4. (Highly Recommended) In the YubiKey Manager, set a FIDO2 PIN. This protects your key if it’s lost and is required by many services.
5. Register the YubiKey with your accounts (Apple, Google, Microsoft, etc.) as required.
6. Finally, test before relying on it. To do so, log out and back in to at least one service to confirm the YubiKey works as expected.

Once you’ve done this, your YubiKey is fully functional for everyday authentication on macOS. The most important part is registering it with the services you actually use—everything else is just fine-tuning for convenience and extra security.

You can forget about System Settings > Privacy & Security, and the, System Information items I mentioned. I confirmed neither will show the key when it is inserted. BTW, you can access System Information by first holding down the <option> key, and then, selecting System Settings... under the Apple logo in the macOS menu bar.

i have a 9th and 11th gen standard ipads, along with an 2018 imac & 2024 m4 mac mini (for plex only). i use the ipads at least 75% of the time. i already have the yubikey 5ci (not used yet) for the ipads and wonder if a security key c (link below) is a good choice for my 2nd key, to use with the imac? just a basic user on the imac. i’m new at this, so ask if you need more info to advise.

https://www.amazon.com/gp/product/B0BVNRXFHT/ref=ox_sc_act_title_1?smid=A3PIGE6HBK2LA8&psc=1

You're very welcome! I'm glad you got it worked out.