Thredded: A new lightweight forums engine for Rails

Thredded is a Rails 4.2+ (yes! - it’s ready for Rails 5) forum/messageboard engine. Its goal is to be as simple, feature rich, and approachable as possible.

By “simple” we mean that it is a quick and easy way to extend an existing rails app with an forum engine instead of spinning up a whole other app like discourse - no docker needed, no extra heroku dynos, no knowledge of ember needed. It is easily theme’able, configurable, well tested, and has a long history with its maintainers (15 years and many rewrites/evolutions).


How easy is it to extend within your rails app? For example, if I wanted to use it, or portions of it behind a paywall, for example?

Easy, config/initializers/thredded.rb:

Rails.application.config.to_prepare do
  Thredded::ApplicationController.module_eval do
    before_action :paywall
    def paywall
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We’ve just released Thredded v0.5.0 with two new major features: topic subscriptions and a basic moderation system.

It took a while to get the foundation right, but now it’s a pleasure to build upon. :slight_smile:


We’ve just released Thredded v0.7.0 with configurable topic list display (ordering, listing followers) and improved moderation, as well as a suite of UI enhancements and bug fixes.


Check out the updated homepage!.

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We’ve just released v0.8.2 with some major new features:

  • More granular user notification settings.
  • Autocompletion for @-mentions.
  • Turbolinks 5 support, and async and defer script loading support for maximum performance.
  • View hooks that let your app and plugins easily extend Thredded views.
  • A Code Syntax Highlighting plugin.
  • A BBCode markup plugin.
  • An app generator that generates a fully-configured Rails app with Thredded and Devise.

Check out the new demo at!


Thredded got several releases since I last posted here. The highlights are:

  • A notifications plugin system, so you can notify about new posts e.g. on Slack.
  • Many improvements to Private Messages.
  • Spanish and Polish localisation.
  • Preview-as-you-type.

And finally, the feature I’m very excited about, a plugin that renders TeX math via KaTeX. The rendering happens server-side for maximum accessibility and performance. This is achieved by calling KaTeX (written in JavaScript) from Ruby via ExecJS.

This is what it looks like:

The updated demo is up at

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Thredded again has received some major improvements since I last posted here.


  • Oneboxes: URLs to supported resources placed on their own line are replaced with a “onebox”.
    Oneboxes replace the previous YouTube and Vimeo implementations and add support for dozens more sites, including Tweets, Google Maps, and so on. The implementation is powered by the onebox gem. #545

  • Auto-follow all new topics setting. #488 #554

    follow screenshot1
    follow screenshot2

  • Email styles: the emails now come in style.
    In the emails, interactive content (such as Google Maps, YouTube Videos) is shown as a static image. #550

  • UI improvements. Messageboards are displayed in a grid on desktop. Post action are now in a dropdown menu (JS-free).

  • Various features such as Mark as unread, and Move Topic to another messageboard.

The updated demo is up at

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Thredded v0.12 is out and comes with the “Quote” reply feature!