How to Format and Beautify XML

Problem

Your XML is minified or inconsistently indented, making it hard to read and debug.

Prerequisites

• Understanding of XML structure
• Familiarity with tree-based markup

Steps

1. 1. Validate the XML

   Before formatting, ensure the XML is well-formed: all tags are closed, attributes are quoted, and there is a single root element. Malformed XML cannot be reliably formatted.

   Input

   <root><item>text</item></root>

   Output

   well-formed

2. 2. Apply indentation and line breaks

   Add a newline after each element and indent child elements relative to their parent. Use a consistent indent size (2 or 4 spaces). Self-closing tags and text content should be handled appropriately.

   Input

   <root><item>text</item></root>

   Output

   <root>\n  <item>text</item>\n</root>

3. 3. Preserve significant whitespace

   XML has both significant and insignificant whitespace. Elements with xml:space="preserve" or mixed content must keep their whitespace. A good formatter respects these rules and does not alter significant whitespace.

   Input

   formatted XML

   Output

   readable, whitespace preserved

Expected result

A well-formed, consistently indented XML document that is easy to read and edit.

Common errors

Formatting breaks mixed content

Mixed content (text interspersed with elements, as in XHTML) has significant whitespace. Use a formatter that preserves mixed content whitespace.

Output is not well-formed

The input XML had errors. Fix the source XML before formatting.

Troubleshooting

• If the formatter changes the meaning of the document, check whether it normalized whitespace in a preserve context.
• Use an XML validator first if the formatter fails.

Security limits

• Formatting does not execute XML. However, parsing XML with DTD enabled can trigger XXE attacks. Use a safe parser.