HDMI 2.0
Direct Answer
HDMI 2.0, released September 4, 2013, raised maximum bandwidth to 18 Gbps, finally enabling 4K resolution at 60Hz. It also increased maximum audio to 32 channels; HDR support followed later via the HDMI 2.0a update in 2015, not the original 2.0 release.
Source: HDMI 2.0 Specification
Specs
| Release Date | September 4, 2013 |
| Max Bandwidth (raw / video) | 18.0 / 14.4 Gbps |
| Max Resolution | 3840x2160 (4K) @ 60Hz |
| Max Audio Channels | 32 |
The Version That Made 4K60 Real
HDMI 2.0 raised total bandwidth from 1.4's 10.2 Gbps to 18 Gbps, finally providing enough headroom for 4K (3840x2160) at a full 60Hz -- the resolution/refresh combination 1.4 could only manage at 24-30Hz. To fit within that bandwidth, HDMI 2.0 relies on 4:2:0 chroma subsampling at 4K60 rather than full 4:4:4 color sampling, a tradeoff invisible for most video content but a real limitation for text-heavy PC use at that resolution and refresh rate.
HDMI 2.0 also raised maximum audio to 32 channels and added support for dual video streams and up to four simultaneous audio streams, along with Rec. 2020 wide color gamut support and a wider 21:9 aspect ratio option for ultrawide displays.
Notably, base HDMI 2.0 did not include HDR support -- that arrived via the HDMI 2.0a update in April 2015, which added HDR10-style static-metadata HDR signaling on top of the same 18 Gbps bandwidth.