Any YouTube creator will tell you that choosing the right thumbnail is a big part of what drives views, and therefore success, on their channels.

There are dozens of articles examining the psychology behind clickbait thumbnails, but the answer remains the same: they work. That’s why some creators were left frustrated by a statement YouTube’s team made on Twitter last night, which announced an experiment on a very small group of select channels to test automated thumbnails for research purposes.

“We are running a small experiment where 0.3% of viewers will see an auto-generated thumbnail, instead of your custom thumbnail,” the tweet reads. “We are not removing the ability to create your custom thumbnail, but we hope to gain insights on auto-generated thumbnails for the future.”

Testing a product for research purposes to only 0.3 percent of a total audience may not seem like that big of a deal, but creators see it as yet another example of YouTube not listening to them.

“YouTube excels at doing things that literally zero people asked for,” comedian ProZD tweeted.

“Jesus christ, I’m sure there’s a youtube guide / handbook where they themselves have said ‘Have a catchy thumbnail, entice your audience’ then they do this,” Martyn Littlewood, a popular creator, also said. “If they removed all my custom thumbnails I’d flip out! (I don’t care how small the percent is).”

“I distinctly remember being taught about the value of a good thumbnail when I went to take a creator class at YouTube HQ, but fuck it, I guess,” creator Claire Rousseau added on Twitter. “Classic YouTube.”

Over-the-top, intriguing thumbnails work. It’s why “YouTube Face,” a term that refers to the exaggerated, often painful looking expression on vloggers’ faces, became a trope a couple of years ago. It’s also why many game channels will include a human face, instead of just a thumbnail of the game — that exaggerated facial expression entices people to click on the video. As pop culture writer Joe Veix wrote for SOMA earlier this year:

At some point, a user discovered that a catchy preview image tended to trigger potential viewers’ curiosity enough that they clicked through more frequently. Most likely this notion was inspired by other forms of clickbait (in style, it seems to be a mix of ~2012 Facebook newsfeed viral garbage with generic chumbox aesthetics). Then another user discovered that including a facial reaction tended to boost views further (perhaps manipulating some kind of primal feeling of empathy or morbid curiosity in the pain of others?). Over time, view count metrics gradually pushed these facial reactions into more exaggerated expressions.

Getting people to click the video in the first place is important, but it’s becoming increasingly difficult on a platform where 450 hours of content is uploaded every minute.

Thumbnails are the first wave of marketing for creators, which helps explain why 0.3 percent of users seeing auto generated thumbnails is a big deal. If there are 1.9 billion logged in users on YouTube every month (a number the company announced last week at VidCon), that means 5.7 million logged-in users will see an auto-generated image. If we assume there are more than two billion monthly users, taking into account those who aren’t logged in, that number rises to 6.3 million.

That’s a lot of eyeballs seeing auto-generated thumbnails, and a large number of possible users who may skip over a video. Creator outrage is understandable once you do the math. It’s a potential loss of views, and that means a potential loss in revenue.

Update: A post on YouTube’s product forums provides a little more insight into the experiment.

“Over the next few weeks, a small group of viewers (0.3% of those on YouTube site-wide) will see the default, auto-generated thumbnail for all videos (across all channels) instead of the custom thumbnail,” the post reads. “For creators, this is the second thumbnail that’s suggested when you upload your video. Note: this will not affect the content of the videos. There are no current plans to change or remove the ability to add custom thumbnails!

“We’re running this experiment to improve auto generated thumbnails (a top request we get from creators who use them) by testing the effectiveness of auto-generated thumbnails.”