Pressflow is a derivative of Drupal core providing enhanced performance, scalability, and data integrity.

Pressflow addresses a long-standing problem: High-traffic sites use stable versions of Drupal, and stable versions of Drupal are ineligible for enhancements to solve performance bottlenecks discovered after widespread deployment.

The Strategy
Leveraging Four Kitchens’ industry-leading experience in scaling high-traffic, Drupal-based sites, Pressflow integrates the most popular enhancements to Drupal core into a single deployable package. All of Pressflow’s enhancements to Drupal core undergo testing by the Four Kitchens team prior to release.

Is Pressflow a fork?
Like Drupal, Pressflow is free, open-source software released under the GNU General Public License, versions two and later, as published by the Free Software Foundation.

Like Ubuntu leverages Debian, Pressflow leverages the success of an existing popular open-source, free software package with enhancements targeting a specific user set. Releases of Pressflow correspond to Drupal core releases and maintain module and theme compatibility.

Following each Drupal core release, Pressflow is “reset,” and all enhancements undergo review. In many cases, new major Drupal releases integrate enhancements that were once exclusive to Pressflow. In such cases, the corresponding Pressflow releases use the standard Drupal implementation to preserve module compatibility. Older major versions of Pressflow continue to support the Pressflow-exclusive implementations.