YouTube is enacting a broad purge of spam accounts over the next two days, and it’s warning creators they could see a big drop in subscribers as a result.

According to YouTube, on Dec. 13-14, creators “may see a noticeable decrease” in subscriber counts. The Google-owned video service regularly works to verify the legitimacy of accounts, and its purge of spammy and bogus users has led to steep declines in sub counts in the past.

“This should help give you confidence that the subs you do have are real fans!” YouTube said in a tweet, with the exclamation mark an apparent effort to put a positive spin on the purge.

YouTube, as part of its quarterly report on enforcement of community standards that first launched earlier this year, said on Thursday it deleted 1.67 million channels during the third quarter of 2018, 80% of which were for spam violations. All told, those channels represented around 50 million videos (which were removed along with the channels).

In addition, in the third quarter YouTube said it deleted 7.85 million videos (81% of which were first detected by automated systems) for violations of its guidelines prohibiting spam and adult content as well as “low-volume areas” like violent extremism and child exploitation. YouTube also removed over 224 million comments for violating community guidelines, most of which were for spam.

YouTube says it’s moving faster to remove objectionable content. It claimed that more than 90% of the videos removed in September 2018 by its automated systems and staff for violations of “violent extremism” or “child safety” rules had fewer than 10 views. Despite its efforts, though, videos that run afoul of YouTube’s policies continue to get past its checks. The world’s biggest video service remains a haven for hate speech and conspiracy theorists, and YouTube even recommends such content, according to a Washington Post investigation this week.

To identify spam accounts, YouTube says it uses a mix of “industry-leading techniques and proprietary technology.” Spammer accounts tend to subscribe to a variety of channels, instead of just subscribing to channels that bought the spam.

YouTube requires channels to have a minimum of 1,000 subscribers to participate in the platform’s ad-revenue sharing program, called the YouTube Partner Program. If the spam-purge causes a channel to drop below the 1,000-subscriber threshhold, it will no longer be eligible for the rev-share program.