The moderators of hundreds of Reddit forums, known as subreddits, closed off access to their groups on Monday to protest the company’s plan to charge for access to the data that outside developers need to run apps on the site.
Many said the new pricing scheme could kill off some of the most popular third-party apps that many users rely on to browse and comment on the site. Others said the charges had sowed uncertainty about the tools that moderators use to manage discussions. An estimated 57 million people a day visit the platform.
Reddit announced in April that it would begin to charge some large-scale users for access to its application programming interface, or A.P.I., the method through which outside entities can download and process the social network’s vast selection of memes, gifs, videos, and conversation threads.
Reddit said it no longer wanted to give away such a valuable asset to companies like Google, OpenAI and Microsoft, which have been using Reddit’s data to develop artificial intelligence systems that many in Silicon Valley see as the next big thing.
“Reddit needs to be a self-sustaining business, and to do that, we can no longer subsidize commercial entities that require large-scale data use,” Steve Huffman, Reddit’s chief executive, said on Friday in an “Ask Me Anything” discussion on the site.
But the charges have set off a major backlash among the volunteer moderators of the site’s diverse communities, who said they would close off access to their groups for at least 48 hours, beginning Monday, in what they called a coordinated protest.
Moderators of some of Reddit’s most popular subreddits — including r/funny, with more than 40 million members, and r/gaming, r/Music and r/science, with more than 30 million members each — were taking part in the protest by setting their pages to private and posting messages denouncing the new terms and pricing.
Moderators of many smaller groups had also gone dark as part of the demonstration.
For a brief period on Monday, the protest made it difficult for some users to access Reddit as “a significant number of subreddits shifting to private caused some expected stability issues,” a Reddit spokesman said, adding that the problems had been resolved.
The developers of several popular apps said they would have to shut them down because of the new pricing system.
Apollo, an iOS app widely praised within the mobile developer community for its design interface and rich features, plans to shut down on June 30, according to a post on Reddit by its developer, Christian Selig. He said that Apollo would have to pay $20 million annually under the new pricing scheme.
“I hope it goes without saying that I don’t have that kind of money or would even know how to charge it to a credit card,” he wrote.
At least three other Reddit apps — rif is fun for Reddit, ReddPlanet and Sync — also announced plans to shut down on June 30, citing what they called unreasonable costs, the tech news site The Verge reported.
The moderators of r/blind, a hub for blind and visually impaired users with more than 20,000 members, said the charges could threaten the third-party apps that translate Reddit text into speech and that allow blind and visually impaired users to participate in discussions on the site.
Noah Carver, one of the r/blind moderators, said in a statement on behalf of his group: “The proposed changes to Reddit’s A.P.I. will not only isolate blind users from a social network used by millions of people, thus disconnecting us from the wider world; they will also largely decimate communities for blind people — and disabled people in general — which have thrived on Reddit despite the company’s perceived indifference.”
Since its founding in 2005, Reddit has been known for embracing freedom of speech, freedom of code and freedom of data, which allowed users to build tools and apps around the site, said Sarah Gilbert, a postdoctoral associate at Cornell University who studies content moderation and data ethics. She is also a moderator of the r/AskHistorians subreddit, which joined the protest.
Ms. Gilbert said the pricing plan could undermine the platform’s volunteer-driven culture, which sets it apart from other social media sites.
“It’s not just about people being unhappy that they can’t have their favorite app anymore,” she said in an interview. “It’s about the loss of community or fear of the loss of community.”
Tim Rathschmidt, a Reddit spokesman, said the company had been in contact with various Reddit communities to “clarify any confusion around our Data A.P.I. Terms, platform-wide policies, community support resources, and timing for new moderator tools.”
He said that Reddit spends millions of dollars on internet hosting fees and “needs to be fairly paid to continue supporting high-usage third-party apps.”
“Our pricing is based on usage levels that we measure to be comparable to our own costs,” he wrote in an email.
Mr. Rathschmidt added that some apps are more efficient and require significantly fewer A.P.I. calls and that “Apollo is notably less efficient than other third-party apps.”
“The vast majority of A.P.I. users will not have to pay for access; not all third-party apps usage requires paid access,” he wrote, adding that access is “is free for moderator tools and bots.”
Responding to concerns about accessibility raised by groups like r/blind, Mr. Rathschmidt said that the company had offered exemptions from the new prices to noncommercial apps that address accessibility issues. Several of those developers have signed agreements with Reddit, he said.
