Editing Help:Transclusion (section)

== Advanced concepts ==
{{Main|Help:Advanced transclusion}}<!-- Temporary move of paragraph from lede of this help document to this subsection per discussion at talk (Help talk:Transclusion#Make sense of lede paragraph on parsing and HTML syntax fragments) until such time as [[Help:Advanced transclusion]] is created. Comment 2025-02-18. -->
Transclusion occurs before [[parsing]] and can emit syntax fragments, like HTML entities, to preserve them in the final render. The content being transcluded is processed and embedded before the target page is parsed and fully rendered. When transclusion happens at the HTML layer before parsing, it allows certain content – like syntax fragments such as [[character entity references]] like <code>&#x26;</code> and <code>mp;</code> or specific HTML components – to be inserted in their original form and preserved in the final render. However, this approach may cause pages to render incorrectly or violate the [[principle of least surprise]] for the reader.{{refn|group=lower-alpha|For example, if [[Whitespace character|whitespace]], tabs, and [[newline]] HTML code are preserved without parsing, the final page may display awkward spacing, misalignments, or unexpected breaks. This whitespace is usually added in the source code to improve readability for developers and isn’t intended to appear in the published content.}} It should be used sparingly when cleaner alternatives are not available. Emitting fragments of template syntax, such as opening braces (<code><nowiki>{{}}</nowiki></code>), is unlikely to re-parse correctly as template syntax in the target page, and it is unwise to rely on such behavior unless formally documented.<!--tested on an older MediaWiki, newer versions may re-parse correctly. Dated unknown. -->