Libxslt

libxslt can be used either as library embedded into an application, or via the xsltproc command line tool. The integration into applications is eased by a multitude of language bindings and wrappers. Being written in C, libxslt is a fast and low-resource processor. This makes it a popular choice for DocBook formatting and as standard XSLT processor for programming languages like PHP, Perl or Python.

The WebKit layout engine (used e.g. in the Apple Safari web browser) uses the libxslt library to do XSL transformations.