XML Formatter & Validator

What is this tool?

This XML formatter and XML validator is a free online tool that formats, validates, and minifies XML in your browser. Paste XML in the left panel and use Validate to check for parser errors, Format to pretty-print with configurable indentation (2 or 4 spaces), or Minify to remove extra whitespace and reduce file size. The input panel uses the Monaco editor (the VS Code engine) with XML syntax highlighting and line numbers. You can copy the result, download it as an .xml file, or share via link. All processing runs client-side—your XML is not sent to any server.

Why use an XML formatter and validator?

XML is used in configuration files (Maven, Ant, Android manifests), data feeds (RSS, Atom, Sitemaps), SOAP web services, SVG graphics, and many enterprise APIs. Minified or single-line XML is extremely hard to read and debug. A pretty-print XML tool makes it readable with consistent indentation; a validate XML step catches malformed tags, missing closing elements, or encoding issues before you deploy or integrate. Minify is useful when you need to reduce payload size for storage, transport, or embedding.

Key features

• Validate — Parse the XML using the browser's built-in DOMParser and show parser errors (e.g. unclosed tags, invalid characters, mismatched elements). Valid XML shows a green "Valid" badge.
• Format (pretty-print) — Indent your XML with configurable 2 or 4 space indentation. Preserves structure, attributes, comments, CDATA sections, and processing instructions.
• Minify — Collapse whitespace between tags and normalize spaces to reduce file size. Ideal for embedding XML in other formats or reducing storage.
• Indent size selector — Choose 2 or 4 spaces when formatting. Preference is applied instantly.
• Live validity indicator — The input panel header shows a green "Valid" or red "Invalid" badge as you type, before you click any button.
• Monaco editor — Both input and output use Monaco (the VS Code engine) with XML syntax highlighting, line numbers, and word wrap.
• Copy — Copy the output (validated, formatted, or minified) to the clipboard with one click.
• Download — Download the result as an .xml file.
• Share — Generate a link that encodes the input XML (base64 in the URL fragment) so you can share the same XML with others. Opening the link restores the input.
• 100% client-side — Your XML is not uploaded to any server. Parsing, formatting, and minification all happen in the browser.

How this tool works (step-by-step)

1. Paste your XML — Paste your XML into the left panel. Use "Load sample" to try it with example data. The panel shows a live validity badge.
2. Validate — Click Validate to check for syntax errors. The tool uses the browser's DOMParser; any error message (with the affected node/line) is shown in the output area.
3. Format or Minify — Click Format to pretty-print with your chosen indentation (2 or 4 spaces), or Minify to strip unnecessary whitespace.
4. Review the output — The formatted, minified, or validated result appears in the right panel with syntax highlighting.
5. Copy, download, or share — Copy the result to the clipboard, download as .xml, or use Share to get a link that encodes your XML.

Real-world examples with code snippets

Minified XML → formatted

Paste single-line or minified XML (e.g. from an API response). Click Format and choose 2-space indent:

// Input (minified):
<catalog><book id="1"><title>XML Guide</title><price>29.99</price></book><book id="2"><title>XSLT</title><price>39.99</price></book></catalog>

// Output (formatted, 2-space):
<catalog>
  <book id="1">
    <title>XML Guide</title>
    <price>29.99</price>
  </book>
  <book id="2">
    <title>XSLT</title>
    <price>39.99</price>
  </book>
</catalog>

Catching common XML errors

Click Validate to find syntax problems before importing into a system:

// Input (invalid — unclosed tag):
<root>
  <item>Hello
  <item>World</item>
</root>

// Validation result:
✗ Error: Opening and ending tag mismatch: item line 3 and root

Minifying XML for embedding

Use Minify to strip all unnecessary whitespace when you need to embed XML in a string, store it compactly, or reduce API payload size. The minified output is a single line with no extra spaces.

Use cases

Best practices for working with XML

• Always validate before deploying — A single unclosed tag or unescaped ampersand can break an entire XML pipeline. Validate first, fix errors, then deploy.
• Use consistent indentation — Pick 2 or 4 spaces and stick with it across your project. Use this tool to enforce a consistent style.
• Escape special characters — XML requires escaping <, &, >, ", and ' in text content. Use CDATA sections for large blocks of unescaped text.
• Minify only for production — Keep formatted (readable) XML in version control and documentation. Minify at build time or when sending over the wire.
• Use CDATA for embedded code — When XML contains HTML, JavaScript, or other code, wrap it in <![CDATA[ ... ]]> to avoid escaping every special character.
• Check encoding — Ensure your XML declaration specifies the correct encoding (usually UTF-8). Mismatched encoding causes parse failures.

Common mistakes & how to avoid them

• Unescaped ampersands — a & b is invalid XML. Use a & b or wrap in CDATA.
• Unclosed or mismatched tags — Every <tag> needs a matching </tag> or self-closing <tag />. The validator will catch these.
• Pasting HTML instead of XML — HTML allows unclosed tags (e.g. <br>, <img>). XML does not. Use the HTML Preview or Minify tool for HTML content.
• Missing XML declaration — While not always required, adding <?xml version="1.0" encoding="UTF-8"?> is a best practice and prevents encoding issues.
• Case sensitivity — XML tags are case-sensitive: <Item> and <item> are different elements. Ensure opening and closing tags match exactly.

FAQ

Related terms

This tool is commonly searched as XML formatter, XML validator, format XML online, pretty print XML, XML beautifier, XML minifier, validate XML online, XML lint, XML checker, XML indenter, and XML pretty printer. It handles formatting, validation, and minification of any XML document—from SOAP responses to Maven pom.xml to RSS feeds—all without leaving the browser.

Similar tools

You might also find these developer tools useful:

• JSON Formatter
• HTML Preview
• Code Minifier
• HTML Entities
• JSON ↔ YAML

Conclusion

An XML formatter and XML validator is essential for anyone working with XML—whether it's SOAP services, RSS feeds, Maven configs, SVG files, or Android manifests. This tool lets you validate structure, pretty-print with configurable indentation, and minify for production—all in the browser with no uploads, no sign-up, and no software to install. For JSON formatting use the JSON Formatter; for HTML use the HTML Preview or Minifier.