XML (eXtensible Markup Language)

XML, eXtensible Markup Language, is a markup language designed for storing and transporting structured data in a format that's both human-readable and machine-readable. It uses custom tags, defined by the person creating the document, rather than a fixed, predefined set.

XML vs. HTML

• HTML — uses a fixed, predefined set of tags specifically for displaying content in a browser
• XML — allows entirely custom tags, focused purely on structuring and transporting data itself

Where XML Shows Up in WordPress

• XML sitemaps — listing a site's pages for search engines to properly discover
• RSS feeds — an XML-based format for distributing recently published content
• WordPress export files — using XML to package up an entire site's content for migration

A Simple XML Example

`<post><title>My First Post</title><author>Ferdy</author></post>` illustrates the general pattern XML follows — custom, genuinely meaningful tags wrapped directly around the actual data they describe.

XML vs. JSON

JSON has largely overtaken XML as the preferred format for most modern web APIs, thanks to being lighter and generally simpler to parse. XML still remains standard specifically for sitemaps, RSS feeds, and WordPress's own native import/export functionality.