Saxon is an XSLT and XQuery processor created by Michael Kay and now developed and maintained by his company, Saxonica. There are open-source and also closed-source commercial versions. Versions exist for Java, JavaScript and .NET. The current version, as of January 2023, is 12.0. Versions The original development line of Saxon ended with the version 6 series. This is a series of XSLT 1.0 processors. The current version, 6.5.5, is not undergoing further development aside from maintenance. The 6 series is only available for the Java programming language. The current development line, Saxon 12, implements the XSLT 3.0 and XQuery 3.1 specifications. Saxon 12 can process XSLT 1.0 and XSLT 2.0 stylesheets. (XSLT 2.0 and 3.0 are highly backwards compatible with XSLT 1.0.) and also includes selective support for the proposed XSLT 4.0 specification. There are two separate source bases: the Java source, and the JavaScript source. The Java source is used to generate products for three platforms: SaxonJ (for Java and other JVM languages such as Scala), SaxonCS (for C# and other .NET languages such as VB.NET), and SaxonC (with APIs for C, C++, Python, and PHP). The JavaScript source base is used to generate SaxonJS, which runs in Web browsers and under Node.js. The Java-built versions come in three levels: Home Edition offers the minimal level of standards conformance defined in the specifications, as an open-source product. Professional Edition adds vendor-specific functionality not required by the standards, for example a range of extension functions and serialisation options. Enterprise Edition adds advanced features (defined in the W3C standards as optional) including schema-awareness and streaming, as well as performance-related features such as multi-threaded execution and bytecode generation. The SaxonCS product is built from the Java source base by means of a custom Java-to-C# transpiler written in XSLT (see https://markupuk.org/webhelp/index.html#ar04.html). As of April 2022, only the Enterprise Edition is offered on this platform. From 2004 until 2009, Saxon was available into two separate forms: Saxon-B and Saxon-SA. Both of these were built on similar codebases. Saxon-B was open-source software released under the Mozilla Public License, while Saxon-SA was a closed-source commercial product. The difference between Saxon-B and Saxon-SA was that B was "basic" while SA was "schema-aware". These terms are references to terms in the XSLT 2.0 and XQuery 1.0 specification. A processor that is "schema-aware" is able to use a W3C XML Schema to define the data types of the