Woodstox is a high-performance XML processor. It implements StAX (Streaming Api for Xml, JSR-173), and supports XML 1.0 and 1.1(including full DTD validation), XML Namespaces 1.0 and 1.1. In addition to core Stax 1.0 API, Woodstox has extended API for pluggable bi-directional validation, both using DTDs (in-built), and external validation modules (for Relax NG, W3C Schema, using Sun MSV).

With version 3.2 Woodstox also implements SAX API for improved interoperability.