SMF - Which version of SMF should I use

The current stable version, at download.simplemachines.org, is always recommended. This version has been tested and declared stable. It also has all the latest features and security enhancements. Please read the client and server requirements, for more information on installation requirements, in order to make certain your server will be able to run the current stable version of SMF. If you are preparing to install SMF for the first time, you should install the current stable version.

For forums running earlier branches of SMF, the current stable version of that branch is recommended. This version has the latest available security features. For more information, please read about Installing, Upgrading, and Patching SMF. If you wish to convert from another forum system to SMF, please also read about Converting to SMF.

Current Stable Version
The current stable versions are.

Older versions of the current series
If you are running an earlier version in the current series it is recommended that you upgrade to the current stable version as soon as possible. The current stable version has all the latest security enhancements, features, and bug fixes. To bring your forum to the latest version in the current series, your options may include:
 * Package Manager Updates, if you are using the previous version in the series. Available from Package Manager Updates. If this works, it will retain your installed mods.
 * Large Upgrade, if you are using an earlier version in the series, or your mods give you trouble. Available from download.simplemachines.org. Uninstall all mods before you start, and reinstall them afterwards.
 * Full Install, if all else fails. This is available from download.simplemachines.org. Reinstall all mods afterwards.

Supported series
The only supported series at this time is

Obsolete series
The .x series is no longer supported, except for requests to help to upgrade to the current stable version. Upgrading to the current stable version is highly recommended for security reasons. Even if this is difficult because of modifications and other customizations, upgrading to the current stable version is required to make a forum safe.

To bring a .x series forum up to the latest version, please upgrade.

The .x series is obsolete and is no longer supported at simplemachines.org. It is recommended that the administrator obtain any assistance required to upgrade to the current stable version. No new features, bug fixes, or security updates will be released for the .x series. While obsolete series can be found in the SMF archives, they are recommended only for reference when preparing to upgrade to the current stable version.

Please upgrade to bring your files and database up to date.

Development versions
Development versions (beta or RC) are not recommended for live SMF forums, as they are still being tested. Interested admins may install development versions, in order to familiarize themselves with new features and options for users and administrators, and for testing. They are available at download.simplemachines.org. Many of your favorite mods may not be compatible with the development versions of the forum. Check your mods' support threads for more information on mods.