View-through rate (VTR) in YouTube ads means the percentage of people who watched your skippable ad all the way through compared to the number of people who saw the ad start.
It’s calculated as:
VTR = (Completed Views ÷ Impressions) × 100
So, if someone didn’t skip your ad and watched it to the end, that counts toward your VTR, it’s a key metric to understand how engaging or effective your video ad really is.
