What does it mean if a subreddit is 'going dark'?

Setting a subreddit to private, aka “going dark,” will mean that the communities taking part will be inaccessible by the wider public while the planned 48-hour protest is taking place. As a Reddit post about the protest, that’s since been cross-posted to several participating subreddits, explains:

How many Subreddits are going dark?

Nearly 7,000 subreddits, some with tens of millions of subscribers, will be switched to private by their moderators starting on June 12. Some of the biggest communities that are going dark include: Thousands of other subreddits have also signed up to participate in the protests.

Why is Reddit going dark?

From June 12 to June 14, thousands of Reddit communities, also known as subreddits, are going dark to protest planned API changes that would essentially kill off many third-party applications. Self-proclaimed as the “front page of the internet”, Reddit is among the top 20 most popular websites and has an estimated 430 million monthly active users.

Will subreddits go dark on June 12th?

On June 12th, many subreddits will be going dark to protest this policy. Some will return after 48 hours: others will go away permanently unless the issue is adequately addressed, since many moderators aren’t able to put in the work they do with the poor tools available through the official app.