Mac storage basics · iPhone and iPad backups and updates
Can I back up my iPhone to my Mac over Wi-Fi?
Short answer: Yes — connect once, tick Show this iPhone when on Wi-Fi in Finder and Apply. On the same network you can then use Back Up Now without a cable, though it's slower.
Yes, after one cable setup. Connect the iPhone, select it in Finder, tick Show this iPhone when on Wi-Fi on the General tab and click Apply. Afterwards, when both are on the same network, the iPhone appears in Finder and you can click Back Up Now without a cable.
Wi-Fi backups are slower than over a cable, especially the first one.