How to Use XML Formatter

Key Takeaways

Well-formed XML follows the structural rules: every opening tag has a closing tag, tags are properly nested, attribute values are quoted, and there is exactly one root element

Well-formed means syntactically correct XML

2-space, 4-space, or tab indentation

The browser-based formatter handles files up to a few MB well

What is XML Formatter?

XML Formatter takes raw, minified, or inconsistently formatted XML and outputs clean, consistently indented, well-formed XML. It also validates structure, highlights syntax errors with line numbers, and can minify XML for production use.

The formatter checks well-formedness only — it does not validate against an XML Schema (XSD) or DTD. For schema validation, use a dedicated XML editor.

Formatter Modes

Beautify

Adds consistent indentation and line breaks. Choose 2-space, 4-space, or tab indentation.

Validate

Checks well-formedness — mismatched tags, unclosed elements, bad attribute quoting. Shows error line numbers.

Minify

Strips all whitespace between elements for the smallest possible XML payload size.

Paste XML

Paste any XML — minified, verbose, or inconsistently formatted.

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Check validation

Well-formedness errors appear immediately with the line number and element causing the problem.

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Choose indent

Select 2-space, 4-space, or tab indentation in settings.

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Copy result

Copy the formatted or minified XML for use in your code, config file, or API tool.

Common XML Errors

Error	Cause	Fix
Mismatched tags	`<a>...</b>`	Ensure closing tag matches opening tag
Unquoted attribute	`<tag attr=value>`	Add quotes: `attr="value"`
Multiple roots	Two top-level elements	Wrap in a single root element
Unclosed tag	`<item>text`	Add `</item>`
Invalid characters	`&` in content	Escape as `&`

Tips & Common Mistakes

CDATA sections for unescaped content. If you need to embed HTML or other markup inside an XML element, wrap it in <![CDATA[...]]> to avoid escaping every < and & character.

XML is case-sensitive. <Item> and <item> are different elements. Mismatched case is one of the most common sources of well-formedness errors.

JSON to XML — convert JSON data to XML
JSON Formatter — equivalent tool for JSON
JSON Validator — validate JSON structure

Frequently Asked Questions

What does 'well-formed XML' mean?

Well-formed XML follows the structural rules: every opening tag has a closing tag, tags are properly nested, attribute values are quoted, and there is exactly one root element.

What is the difference between well-formed and valid XML?

Well-formed means syntactically correct XML. Valid means it also conforms to a specific schema (DTD or XSD). The formatter checks well-formedness; schema validation requires a schema file.

What indentation options are available?

2-space, 4-space, or tab indentation. Choose based on your project's coding style.

Can it handle very large XML files?

The browser-based formatter handles files up to a few MB well. For very large files (10 MB+), a local XML editor or command-line tool (xmllint) is more appropriate.

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