Trainor oversaw Vimeo for four years as the video-upload site grew and morphed to allow options like subscriptions, but the site remains a distant second to main rival YouTube
The CEO of Vimeo's parent company, IAC, will serve as interim chief after Trainor departs.
Vimeo CEO Kerry Trainor is leaving the online video upload site, a smaller rival to Google's YouTube.
In a memo to staff Tuesday, Trainor said he was "stepping back" from Vimeo, though he will remain an advisor there as the chief of parent company IAC, Joey Levin, serves as interim CEO.
Vimeo is often known as a high-brow YouTube. Like Google's video site, Vimeo lets people upload clips. But its early dedication to high picture quality and ban on video ads, means it's more likely to host film-festival fodder than cat clips.
Trainor served as CEO for four years, a period when Vimeo grew significantly but remained far behind YouTube; Google's site has well over a billion monthly users to Vimeo's 280 million.
"My plan now is to live life for a bit while working with a few companies as a board member until I'm ready to announce my next full time project," Trainor said.