{{ define "title" }}XSLT & Saxon Error Reference — common errors explained with fixes | {{ .Site.Title }}{{ end }} {{ define "main" }}
The most common XSLT and Saxon error codes and parser messages, explained in plain English: what each error means, what typically causes it, and how to fix it — with before/after examples you can verify in the online XSLT editor.
Saxon error codes follow the W3C convention: XPST (XPath static), XPDY (XPath dynamic), XPTY (XPath type), XTSE (XSLT static), XTDE (XSLT dynamic), FO* (function library). Parser messages such as "Content is not allowed in prolog" come from the underlying XML parser and mean the input is not well-formed XML. Also see the XSLT & XPath function reference.