It’s the first major Apache web server update since the 2.2 release in 2005. A key focus in the 2.4 release is improved performance which is delivered by way of multiple innovations.
Core enhancements that revealed by its official site:
- Loadable MPMs Multiple MPMs can now be built as loadable modules at compile time. The MPM of choice can be configured at run time.
- Event MPM The Event MPM is no longer experimental but is now fully supported.
- Asynchronous support Better support for asynchronous read/write for supporting MPMs and platforms.
- Per-module and per-directory LogLevel configuration The LogLevel can now be configured per module and per directory. New levels trace1 to trace8 have been added above the debug log level.
- Per-request configuration sections <If>, <ElseIf>, and <Else> sections can be used to set the configuration based on per-request criteria.
- General-purpose expression parser A new expression parser allows to specify complex conditions using a common syntax in directives like SetEnvIfExpr, RewriteCond, Header, <If>, and others.
- KeepAliveTimeout in milliseconds It is now possible to specify KeepAliveTimeout in milliseconds.
- NameVirtualHost directive No longer needed and is now deprecated.
- Override Configuration The new AllowOverrideList directive allows more fine grained control which directives are allowed in .htaccess files.
- Config file variables It is now possible to Define variables in the configuration, allowing a clearer representation if the same value is used at many places in the configuration.
- Reduced memory usage Despite many new features, 2.4.x tends to use less memory than 2.2.x.
A bulk of module enhancements have implemented as well, which can be referred at the New Features page.