About XML Formatter & Validator
Comprehensive Overview
The XML Formatter & Validator helps developers format messy XML into clean, properly indented documents, validate XML structure, and minify XML for production. Whether you're working with configuration files, API responses, SVG graphics, RSS feeds, or sitemaps, this tool provides instant formatting with clear error detection.
Key Features
- Format & Beautify — Transform compact or poorly formatted XML into a readable structure with consistent indentation (4 spaces per level).
- Validate — Check XML for well-formedness errors: unclosed tags, mismatched elements, invalid characters, and malformed attributes. Error messages include line numbers.
- Minify — Remove all unnecessary whitespace between elements to reduce file size for production deployment or network transfer.
- Universal Support — Works with any valid XML: SVG files, XHTML pages, RSS/Atom feeds, sitemaps, SOAP messages, configuration files, and custom schemas.
How to Use
- Paste your XML into the input field.
- Select the action: Format to beautify, Minify to compress, or Validate to check structure.
- Click Process to see the result. Errors (if any) appear with line numbers for quick debugging.
Technical Background
The tool uses PHP's DOMDocument class with libxml for parsing and validation. Libxml is the same XML parser used by major web browsers and server software, ensuring reliable results. When formatting, preserveWhiteSpace is set to false and formatOutput to true, producing consistent 4-space indentation. Error detection captures all libxml warnings and errors, providing detailed messages with line and column numbers.
Common XML Errors
- Unclosed tags — Every opening tag must have a matching closing tag (e.g.,
<div>...</div>) or be self-closing (<br/>). - Mismatched tags — Tags must be properly nested:
<a><b></b></a>is valid,<a><b></a></b>is not. - Unescaped special characters — Characters
<,>,&must use entity references inside content. - Missing XML declaration — While optional,
<?xml version="1.0" encoding="UTF-8"?>is recommended.