libxslt

libxslt is a C library that implements an XSLT processor and is part of the libxml2 project. It provides a C API for embedding XSLT transformations in applications and a separate command-line tool, xsltproc, that applies stylesheets to XML documents. The library relies on libxml2 for parsing and tree construction.

libxslt implements the XSLT 1.0 specification and offers broad support for templates, parameters, keys, and the various XSLT instruction sets. It uses XPath for navigation and selection within documents and supports output control, including indentation and method selection. The processor can be extended with user-defined functions and extension elements, and it includes support for EXSLT extensions used by many stylesheets.

As an embeddable library, libxslt exposes an API that allows applications to compile stylesheets, manage transformation parameters, and apply stylesheets to input documents, producing a result tree that can be serialized. The accompanying xsltproc tool provides a ready-to-use transformation workflow with options for debugging, parameter passing, and output formatting.

libxslt originated within the libxml2 project and has been maintained by Daniel Veillard and contributors. It is distributed under a permissive license (MIT/X11-style), making it a common choice in Linux distributions, GNOME software, and other open-source ecosystems. It is often used indirectly through bindings such as Python's lxml library.

See also: libxml2, xsltproc, EXSLT, XSLT.