YouTube Premium, an ad-free subscription service that bundles video and music access, has been available for several years. Despite it recently reaching 100 million subscribers, YouTube continues to battle the widespread use of ad-blocking technology, hoping to drive more subscriptions to the Premium tier.

Last year, YouTube began aggressively targeting ad blockers on desktop platforms. In the latest escalation, YouTube announced a crackdown on mobile ad blockers. “We only allow third-party apps to use our API when they follow our API Services Terms of Service,” an official blog post stated. “When we find an app that violates these terms, we will take appropriate action to protect our platform, creators, and viewers.”

Users who attempt to watch videos through third-party apps designed to circumvent YouTube ads may now encounter errors, such as excessive buffering or messages stating, “The following content is not available on this app.”

YouTube justifies this move by explaining, “Our terms don’t allow third-party apps to turn off ads because that prevents the creator from being rewarded for viewership, and ads on YouTube help support creators and let billions of people around the world use the streaming service.”

With increasing restrictions on ad-blockers across devices, YouTube is sending a clear message about YouTube Premium being the only way to watch YouTube ad-free.