Use the YubiKey Personalization Tool to configure the two slots on your YubiKey on Microsoft Windows, Mac (macOS and Mac OS X), and Linux operating systems. The tool works with any YubiKey (except the Security Key). You can also use the tool to check the type and firmware of a YubiKey, or to perform batch programming of a large number of YubiKeys. In addition, you can use the extended settings to specify other features, such as to disable fast triggering, which prevents the accidental triggering of the nano-sized YubiKeys when only slot 1 is configured.
(This tool works on all Yubico devices except the FIDO U2F Security Key, the Security Key by Yubico, and the Security Key NFC by Yubico.)
YubiKey Personalization Tool (preferred) v3.1.25
YubiKey Personalization Tool (command line interface) v1.19.0