HDCP was originally developed by Intel engineers but gradually became common throughout the technology and entertainment industries. HDCP often gets confused with HDMI, and while they’re related they obviously aren’t the same. HDCP provides copy protection and piracy prevention for three main connection types, including HDMI. The other two are DVI and DisplayPort. So, while you shouldn’t confuse HDCP with HDMI just remember that ALL of your devices and cables must be HDCP compliant to enjoy 4K content, since HDMI has become virtually universal. By devices we mean source (streaming box, Blu-ray, PC, game console, HDMI splitter, and others), cables, and accepting device – your projector, TV, or monitor. If even one component lacks HDCP certification, content won’t play in 4K or may not play at all. You also need to have the same version of HDCP on all components or else you’ll get downgraded full HD content and not 4K. The relevant version is HDCP 2.2 as of this writing.
Remember that if you have a smart TV or projector and stream content directly from their operating system without any external devices or cables (i.e. from built-in apps), then HDCP doesn’t apply. It only comes into play (pun alert) when connecting various devices via cables.
Another note: the video game industry hasn’t taken up HDCP, instead developing various other protection mechanisms such as Denuvo. So if you just want to hook up an Xbox or PlayStation to a 4K display for games ONLY, then you don’t need to worry about HDCP.