YouTube is on a massive sweep of spam accounts, and the company is alerting creators that they may see a “noticeable decrease” in their subscriber counts as the cleanup is conducted.

An official post on YouTube’s product forum states these sweeps are part of routine maintenance the company performs. Removing spam accounts helps to keep YouTube “a fair playing field” for creators, since they can artificially increase a channel’s subscriber count. It’s unclear how many channels will be affected, but YouTube does want people to prepare for a decline.

“We regularly verify the legitimacy of accounts and actions on your YouTube channel,” the blog post reads. “As part of these regular checks, we identified and will remove a number of subscribers that were in fact spam from our systems.”

“We regularly verify the legitimacy of accounts and actions on your YouTube channel.”

The blog post specifically states that spam accounts are usually used to make a channel look more popular than it actually is. Major channels like PewDiePie and T-Series may notice a decrease, affecting their ongoing competition, but it’s smaller creators who face the biggest risk, since they could lose their ability to monetize videos.

“Channels that had a high percentage of spam and fall below 1,000 subscribers will no longer meet the minimum requirement for YPP [YouTube Partner Program] and will be removed from the program,” the blog post reads. “They are encouraged to reapply once they’ve rebuilt their subscribers organically.”

The sweep is occurring between today and December 14th. Owners of affected channels will see a banner in YouTube Studio or Classic Creator Studio.