A CL3 rating is very similar to CL2 in the respects that they are both usable in wall, and are both resistant to holding and carrying flames. The main difference between the two is the wattage that a CL3 rated cable can carry.

What are CL3 cables for?

They are both used for Video, Audio Interconnects, remote-control, signaling, and power-limited circuits. In plain English that means that CL2 and CL3 are rating types for most types of low voltage cabling such as: speaker wire, Cat5/6, and HDMI cables.

Does HDMI need to be CL2?

Short answer: Yes, your cable needs to be rated for in-wall use.