XML Syntax and Rules

Estimated study time: 15 minutes.

XML is strict about its syntax. A document that breaks these rules is considered not well-formed, and most parsers will refuse to process it. Here are the rules every XML document must follow.

1. One Root Element

Every document must have exactly one top-level element that wraps everything else.

2. Every Tag Must Be Closed

<!-- Correct -->
<title>Data Analytics</title>

<!-- Incorrect -->
<title>Data Analytics

3. Tags Are Case-Sensitive

<Title>...</title>  <!-- invalid: Title and title don't match -->

4. Proper Nesting

<!-- Correct -->
<a><b>text</b></a>

<!-- Incorrect -->
<a><b>text</a></b>

5. Attribute Values Must Be Quoted

<student id="102">...</student>

6. Special Characters Must Be Escaped

• < for <
• > for >
• & for &
• " for "
• ' for '

7. Whitespace Is Preserved

Unlike HTML, XML parsers preserve whitespace exactly as written inside elements, which matters for text-heavy content.