We investigate the impact of medium of communication (in-person versus video) on intraspeaker variation in conversation—a process we refer to as medium-shifting. To quantify the effects of medium-shifting and understand its possible motivations, we analyze three variables that show intraspeaker effects of “clear” or “careful” speech: articulation rate, density-controlled vowel space area, and (ING). The data come from matched in-person and video-mediated interviews with thirty-three repeat guests from The Late Show with Stephen Colbert, recorded before and during the COVID-19 pandemic. Mixed-effects regression models show that compared to in-person interviews, video-mediated interviews involve a significantly lower articulation rate and larger vowel space, but no significant difference in (ING). The results suggest that speakers may engage in medium-shifting in order to enhance their intelligibility over video, for example, through more precise articulatory movements and greater contrast between phonemic vowel categories. The null effect of medium on (ING) further suggests that medium-shifting is a motivator of intraspeaker differences even within a single contextual style. An emergent extralinguistic factor affecting speaking behavior and choices, medium-shifting should be carefully considered especially when designing variationist research involving mixed media interviews.