Input Lag is not an official television specification and regrettably, you will not find it listed in the specifications for the LG C9 77 inch Class 4K Smart OLED TV w/ AI ThinQ® (76.7'' Diag), Model # OLED77C9PUB nor for any of our other TVs. However, they are online sites that review some of our TVs and they will test them for Input Lag and report it on their sites. They are several methods available for testing Input Lag and the results will vary depending on which Input Lag Testing Method is used. What we specifically announced abut the input lag for our OLED TVs was that "outside of VRR, the TVs will deliver 13 ms input lag in 1080p and 4K HDR". Input Lag will also vary depending on whether it is tested for 1080p @ 60 Hz, 1080p @ 60 Hz Outside Game Mode, 4k @ 60 Hz, 4k @ 60 Hz + HDR, 4k @ 60 Hz @ 4:4:4, 4k @ 60 Hz Outside Game Mode, 4k @ 60 Hz With Interpolation, 1080p @ 120 Hz, 4k @ 120 Hz, 4k with VRR or with with Auto Low Latency Mode (ALLM) switched on. Unfortunately, without a reference to what the reports you have read are reporting the 21 ms for, we cannot verify this.