Thousands of Reddit communities have "gone dark" as part of a protest by users over how the site is being run.

Reddit is introducing controversial charges to developers of third-party apps, which are used to browse the social media platform.

But moderators of some of the biggest subreddits have hit back by making their communities private for 48 hours.

Reddit relies heavily on community moderation but on Monday more than 7,000 subreddits shut down.

A subreddit is the name given to a forum within the Reddit platform - effectively a community of people who gather to discuss a particular interest.

Reddit users - or Redditors - will typically join a variety of subreddits, rather than following individual users on other platforms, and see posts from these communities in their feed.

As well as a few paid administrators, the website uses tens of thousands of unpaid moderators - known as mods - to keep the website functional.

These mods may spend one or two hours per day ensuring that their subreddit does not get filled with off-topic comments, content that is banned, or even content which is illegal.

But the flipside of this is that Reddit does not charge any hosting fees for people who want to set up their own community based on an interest they have.

In a post to the website on Friday, Reddit chief executive Steve Huffman said it "needs to be a self-sustaining business" and addressed the blackout.

"We respect when you and your communities take action to highlight the things you need, including, at times, going private," he said.

"We are all responsible for ensuring Reddit provides an open accessible place for people to find community and belonging."

He also confirmed that explicit content would remain on the site, but Reddit would limit how it can be accessed from third-party apps.