HDMI switchers available for consumers are at least 1080p and Dolby Digital/DTS compatible. If you have a 4K Ultra HD TV and 4K source components, the switcher must also be 4K compatible.

the truth is you don’t need to overspend if your goal is to get 4K resolution at 120Hz. All but one of our picks support the latest HDMI 2.1 standard, ensuring you get the best possible audio ...

Anything older than HDMI 1.4 is now obsolete, and only present on really old gear. HDMI 1.4 is good enough for 1080p SDR equipment. Though it can do 4K/30, and you can still find it on small, cheap ...