This article outlines the general features commonly found in various Internet forum software packages. It highlights major features that the manager of a forum might want and should expect to be commonly available in different forum software. These comparisons do not include remotely hosted services which use their own proprietary software, rather than offering a package for download which webmasters can host by themselves. General information Basic general information about the forums: creator/company, license/price etc. Systems listed on a light purple background are no longer in active development. Features Flat vs. threaded A flat forum is one where each message is added onto the end of the discussion, with no set relation to any prior messages (other than being on the same discussion topic — except in case of Off-Topic posting). But, there is normally a feature to 'quote' another user's post, to allow referencing back to other posts. A threaded forum is one where users can specify their message is a reply to an existing message. Threaded forums can display relationships between message topics and associated replies, such as by indenting replies and placing them below the post they reference. Threaded forums are most commonly used for discussions where individual messages tend to be short, such as on social news sites (e.g. Slashdot or reddit), or in commenting systems like Disqus. User-selectable themes Most forums provide an option for the forum owner to customize the look and feel. Some forums also allow the administrator to create multiple styles or themes, and allow the user to choose which one they wish to view. Themes may simply be a different set of colors and graphics, or they may involve a different layout to the forum, such as one optimized for small-screen devices. The comparison table shows whether a forum software allows forum administrators to customise the "template" of the forum (or specific sections thereof) without altering the released code. Support is considered partial where it is only possible to add CSS rules in this way. Unread message tracking Unread message tracking refers to the way that is used by forum software to track and display messages that have not yet been read by the current user. This can be one of the following: Session — when a user's session starts, this method relies on the user's "last visit time" to display all messages created since that date as unread. Everything that