# Introduction

This page describes how to extend the capability of Saxon XSLT Stylesheets and XQuery queries by adding extension functions and other user hooks.

The first two columns of the table below indicate which sections of this page are applicable to XSLT and which are applicable to XQuery.

XSLT | XQuery | Contents
§ § § § § § § § § | § § § § | Writing extension functions Writing extension instructions Writing input filters Writing output filters Implementing a collating sequence Implementing localized numbers and dates Adding an output encoding Writing a URI Resolver for input files Writing a URI Resolver for output files

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