What forum software should I use?

The Webmasters FAQ outlines the nature of acceptable questions for this site: researching available solutions and providing anecdotal advice falls outside the purpose of this StackExchange site, so this type of question would be better-suited to chat or another discussion forum.

That being said, there are a variety of free and open source content management systems, as well as licensed software and paid services, which may meet your requirements.

Some of the most popular forum scripts include:

• PHPBB (php, free and open source)
  • Pros: it's been around for a long time, so there are lots of documentation and mods for it. Has lots of features.
  • Cons: installing mods is not easy.
• Fluxbb (php, free and open source)
  • Pros: very lightweight and simple
  • Cons: hard to install mods, not a lot of features.
• vBulletin (php, pricing varies by suite)
  • Pros: very robust and powerful, widely used
  • Cons: very expensive
• Vanilla Forums (php, free)
  • Pros: easy to use, with a great user interface
  • Cons: isn't like a traditional forum, and some of the features, like badges, aren't free.
• BBPress (php, free and open source)
  • Pros: plugin version integrates really well with wordpress, simple, seo-friendly urls built in, easy to modify and hack if you know wordpress.
  • Cons: often need to integrate bbpress with your wordpress theme.
• SMF (php, free and open source)
  • Pros: great mods, and a great community
  • Cons: can be hard to customize if you aren't used to the admin interface
• MyBB (php, free and open source)
  • Pros: tons of features
  • Cons: amount of features can be overwhelming
• XenForo (php, commercial)
  • Pros: lots of great features, such as badges.
  • Cons: it's not free.
• Ninja Post (php, commercial)
  • Pros: hosted solution, real time updates.
  • Cons: Not free.
• nodeBB (javascript, open source)
  • Pros: superfast and realtime, built on nodejs & redis
  • Cons: Does't integrate with existing website/user system and difficult to customize.
• Codoforum (php, free)
  • Pros: Modern, Unconventional with rich content support
  • Cons: It is still a very new forum
• IP.Board (php, commercial)
  • Pros: Modern, flexible
  • Cons: Requires core package which is very expensive
• PlushForums (php, commercial)
  • Pros: Easy to use, real-time updates, hosted
  • Cons: Not free
• Flarum (EsoTalk successor) (php, open source)
  • Pros: very sleek and simple interface
  • Cons: early beta

All of the forum software listed above are built around the concept of mods (plugins) which extend the application's functionality - there are many mods, with new mods authored every day.

Sites like forum-software.org can help you compare different forum software, and have forum comparison tools and in-depth reviews.

If you have researched different forum software and available mods but cannot find anything that will meet your needs, you should consult a developer (or do it yourself) who can build something to your specifications either as a mod for an existing forum script or as a stand-alone application.

Discontinued software

Formerly listed here, and for sake of completion moved down instead of removed:

• EsoTalk (php, open source)
  • Pros: Simple, with a sleek interface
  • Cons: ?