The Apache Software Foundation on Thursday released a major upgrade to the hugely popular open-source Apache Web server. New features in Apache 2.2.0 include support for large files and improved caching.

Apache is used to power about 70 percent of websites, according to a recent survey from Internet monitoring firm Netcraft. It is part of the standard open source stack LAMP (Linux, Apache, MySQL and PHP or Perl).

The 2.2.0 release marks the start of a new stable branch, according to developers. "This release has been through extensive testing, including live at some of the world's busiest sites, and is now considered stable," said the organisation in an announcement on Thursday. "This means that modules and applications developed for Apache 2.2.0 will be both source- and binary-compatible with future 2.2.x releases."

The release builds on the Apache 2.0 programming interface, developers said.

The server can now support large files - over 2GB - on 32-bit Unix systems, and can handle large request bodies as well.

Another addition is smart filtering, introduced in the module mod_filter. "It enables filters to be conditionally inserted, based on any Request or Response header or environment variable, and dispenses with the more problematic dependencies and ordering problems in the 2.0 architecture," the announcement said.

The mod_dbd module adds direct SQL database support for modules that need it, the Apache organisation said. The module supports connection pooling in threaded Multi-Processing Modules (MPMs). The database feature hasn't yet been included in the standard Windows build, the group said, and may not be completely stable on that platform.

A complete list of new features is available from the project's website.