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Introduction to XML

Last reviewed May 28, 2026 Content v20260528
Track mode
iframe_xml
Means
XML preview sandbox
Reading
~2 min
Level
beginner

This lesson

An orientation to this XML lesson—scope, vocabulary, and what you will practice next.

You need a clear map of the XML track so later lessons do not feel like isolated tricks.

You will apply Introduction to XML in contexts like: Enterprise integration, publishing pipelines, Android resources, and data exchange alongside JSON.

Edit XML in the playground, watch well-formedness feedback, preview rendered output, then complete the quizzes. Also open the interview prep blocks.

Start here at the beginning of the xml track before skipping ahead.

How this XML track works

  • Beginner — well-formed syntax, elements, attributes, entities; edit XML in the playground.
  • Intermediate — DTD/XSD concepts, XPath queries, feeds (RSS/Atom), and config files.
  • Advanced — XSLT transforms, enterprise patterns, security, and interview prep.

The playground validates as you type and shows a tree preview when the document is well-formed. No separate Run button—fix errors until the validator turns green.

Install on your device (macOS, Linux, Windows)

Lessons run in your browser on this site—install a modern browser and optional editor for local projects.

macOS

  1. Use Safari (preinstalled) or install Google Chrome / Firefox.
  2. Optional editor: VS Code (brew install --cask visual-studio-code).
  3. Open DevTools with ⌥⌘I (Chrome/Edge) or ⌥⌘C (Safari Web Inspector).

Linux

  1. Install Chromium or Firefox: sudo apt update && sudo apt install -y chromium-browser firefox (Debian/Ubuntu; package names vary by distro).
  2. Fedora: sudo dnf install -y chromium firefox.
  3. Optional editor: VS Code from code.visualstudio.com or sudo snap install code --classic.

Windows

  1. Install Microsoft Edge or Chrome.
  2. Optional editor: VS Code (winget install Microsoft.VisualStudioCode).
  3. Open DevTools with F12 or Ctrl+Shift+I.

Verify: Open any lesson playground and click Run—output appears without installing a compiler.

XML (Extensible Markup Language) is a text format for structured data. Unlike HTML, you define your own tag names to model books, invoices, configuration, or syndication feeds.

Why XML still matters

  • RSS and Atom feeds for blogs and podcasts
  • SVG vector graphics (XML syntax)
  • Enterprise APIs — SOAP, SAML, Office Open XML
  • Config — Maven pom.xml, Android layouts, build tools

Playground

Edit the XML below. When the document is well-formed, the validation panel confirms it and the preview shows the browser tree view.

Interview prep

What is XML?

Extensible Markup Language — a text format for structured data with custom tags, stricter than HTML, often used for feeds, config, and enterprise integration.

Well-formed vs valid?

Well-formed follows XML syntax rules. Valid also matches a schema (DTD/XSD).

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Not saved yet.

Playground

Runs in your browser in a sandboxed frame. Backend runners appear when this track’s profile allows them.

Check yourself

Multiple choice — immediate feedback.

Discussion

Past discussion is visible to everyone. Only logged-in users can post comments and replies.

Starter discussion topics

  • What part of this lesson needs a second read?
  • What would you try differently in a real project?

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