Video-sharing platform YouTube has been running a test that places its 4k video-playing capabilities behind its premium subscription.

According to ANI, it has been reported by some users in recent weeks they have been seeing playback of 2160p resolution video restricted with text labeling it as a premium feature.

YouTube has since confirmed via Twitter that those seeing the new restrictions were part of an experiment to better understand the feature preferences of premium and non-premium viewers.

It isn’t clear if YouTube will restrict all non-premium users to 1440p video quality, and the company is directing users to leave feedback on the restrictions for the Google subsidiary to “make improvements.”

A YouTube Premium subscription service grants access to YouTube Music Premium, as well as in-app downloads, background play, and most importantly: ad-free viewing.

YouTube has been known for some fairly aggressive advertising, with 9to5 Google reporting that a previous test saw the company place as many as ten unskippable ads onto a single video.

It was estimated that YouTube had around 2.24 billion global users in 2021, of which only around 50 million were premium and music subscribers.