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Reddit reported 121.4 million Daily Active Uniques for the quarter ended 31 December 2025 in the Form 10-K it filed with the SEC, a 19 percent rise year over year. The machinery under that number is the same machinery a twelve-member hobby board runs: a topic, replies stacked under it in the order they arrived, one address for the whole exchange.
An internet forum is a website, or a section of one, where members post messages under named topics and other members reply to them in place, so the conversation accumulates on a page instead of scrolling past. The unit is the thread. Everything else in a forum is an arrangement of threads, a permission on who may write in them, and a rule about what happens when someone breaks the rules.
Categories, threads and posts
Forum structure runs top down in three or four layers. Categories, sometimes called boards, split the site by subject. Subforums split a busy category further. Inside a category sit threads, also called topics, each one started by a single post. Under the first post come the replies, in chronological order, each with an author, a timestamp and a permalink of its own.
The ordering rule is what separates a forum from most other formats. Threads are listed by the time of their most recent reply instead of their creation date, so a five-year-old thread that gets an answer today returns to the top of its category. That behaviour is called bumping. On top of it sit two overrides an operator controls: pinning, which holds a thread at the top regardless of activity, and locking, which leaves a thread readable but closed to new replies.
The topic-tree shape is older than the web. Usenet, the first large-scale distributed discussion system organised into topic newsgroups, was conceived in 1979 by Duke University graduate students Tom Truscott and Jim Ellis, and Ellis handed out 80 copies of a five-page "Invitation to a General Access UNIX Network" at the January 1980 USENIX conference in Boulder. Newsgroups became categories. Articles became posts.
Members, moderators and administrators
A registered account on a forum is a member, and what that member can do is decided by the role attached to the account. Three tiers are typical. Members read, post, reply and send private messages. Moderators lock, move, split, merge and delete threads, and issue warnings or bans. Administrators hold the settings panel: categories, permissions, themes, integrations, and the ability to delete the board.
The setting that decides the tone of a new forum is the one nobody looks at on day one. Whether a first-time registration can post immediately or waits in an approval queue is a configurable value, and whoever installs the software picks it. The same is true of whether posts from accounts below a post count get held for review. Both are flags. Both are off or on before your first member ever arrives.
Expect most of those members to read and never write. The distribution behind that expectation, and the studies that measured it, are covered in community engagement and the 90-9-1 rule.
Features most forums carry
- Full-text search across the archive, usually with filters by author, category and date
- Quoting, which pulls a passage from an earlier post into a reply and links back to it
- Subscriptions or watching, which notify a member when a thread they follow gets a reply
- Private messages between members, separate from the public categories
- Attachments and inline images, with a size cap set by the operator
- Profiles, post counts and reputation signals such as likes, badges or solved markers
- Tags, which cut across the category tree so one thread can appear in several listings
Who is responsible for what gets posted
In the United States, the liability question is answered by one sentence of federal law. Section 230(c)(1) states that "No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider", as the Congressional Research Service sets out. Codified at 47 U.S.C. § 230, the section is titled "Protection for private blocking and screening of offensive material" in the 2021 edition of the U.S. Code.
Read the text closely and the boundary shows. The shield covers information provided by another content provider, which is the member who typed it. What an administrator writes in their own announcement post is their own speech.
The second half matters more to anyone moderating. Section 230(c)(2)(A) shields services and their users from liability for good-faith action to restrict access to material they consider objectionable, whether or not that material is constitutionally protected, according to the Center for Democracy & Technology's 2026 explainer. Deleting a post does not convert a forum into a publisher of everything left standing. That is the provision the "moderate and you lose your protection" folklore gets backwards.
Two limits on all of this. It is U.S. federal law, so a board hosted for a European or Asian audience sits under a different regime that this statute says nothing about. And the internet these rules were written for was small: when Section 230 passed in 1996, roughly 40 million people used the internet worldwide, according to the Electronic Frontier Foundation.
Forums and blogs
A blog is organised around its authors and a publication date, while a forum is organised around its members and the last reply. On a blog, a new post pushes older posts down the front page whether or not anyone is still discussing them, and comments hang below a piece as a subordinate feature that can be switched off. On a forum, any member can open a thread, and activity decides what sits at the top. The practical difference is who holds the microphone: one writer with an audience, or a few hundred people with equal posting rights. How that difference plays out in search results is the subject of the piece on forum SEO and thread indexing.
Forums and chat apps
Chat and forums both let a group talk, and they fail at opposite things. A Discord or Slack channel is a single stream ordered by time, so a question asked on Tuesday is buried by Wednesday and hard to search back. A forum splits that stream into threads with stable addresses, which is why an answer posted in 2021 can still be found in 2026.
The cost sits on the other side. Chat is faster, and moving out of it is not clean: attachment links expire, exports arrive incomplete, and members do not all follow. What an export contains is covered in archiving a Discord server, and the retention problem in migrating a community from Discord to a forum.
Examples of internet forums
An example of an internet forum is Stack Overflow, where programming questions sit as threads with answers, votes and a marked solution. Other live examples that show the same structure in different registers include the support communities vendors run beside their documentation. Reddit is the same structure at scale, with subreddits as the categories and volunteer moderators as the staff.
Of the forums that publish audited usage figures, Reddit's are the largest.
2025 usage data
In the United States, which is where the regular survey data comes from, the share is rising: Pew Research Center's 2025 survey of 5,022 U.S. adults found 26 percent say they ever use Reddit, up from 18 percent four years earlier. In the same survey YouTube sat at 84 percent and Facebook at 71 percent, so threaded discussion is a minority habit that is growing.
Two other readings sharpen it. Pew's social media and news fact sheet puts the share of U.S. adults who regularly get news on Reddit at 9 percent, against 20 percent each for Instagram and TikTok. And Pew's teens and social media fact sheet records 14 percent of U.S. teenagers aged 13 to 17 using Reddit, against 90 percent for YouTube and 63 percent for TikTok, which is the number to check before planning a forum whose members are supposed to arrive from that age group.