The following software must be installed separately, it is not included with the Saxon download.

By default Saxon uses an XML parser that supports the SAX2 interface. Saxon has been tested successfully in the past with a wide variety of such parsers including Ælfred, Xerces, Lark, SUN Project X, Crimson, Piccolo, Oracle XML, xerces, xml4j, and xp. By default, however, it uses the parser that comes with the Java platform (this is Crimson in the case of JDK 1.4, Xerces in the case of JDK 1.5). The parser must be SAX2-compliant. All the relevant JAR files must be installed on your Java CLASSPATH.

Earlier releases of Saxon included a version of the Ælfred XML parser. This version is no longer bundled with the Saxon distribution on Java platforms, because JDK 1.4 now includes an XML parser as standard. However the Saxon version of the Ælfred XML parser remains available as a separate download from the Saxon site at SourceForge. (Note that this version is not identical to the one that is included in GNU Classpath, which now forms part of the Saxon distribution on the .NET platform).

Saxon's DOM interface has been tested with the Crimson parser included as standard in Sun's JDK 1.4 platform and with the Xerces DOM implementation included in JDK 1.5. It has also been used successfully with other DOM implementations such as Oracle's, though it is not routinely tested in this environment.

Saxon will also work with a StAX parser. Generally speaking, StAX parsers are currently less mature than SAX parsers, and any performance advantage is likely to be very minor. However, the support for StAX provides the ability to supply input via a customized pull pipeline. Saxon is tested with Woodstox 3.0.0. Saxon's schema validation is available only with a SAX2 parser.