XML Formatter & Validator

How to use the XML Formatter & Validator

1. •Paste your XML content into the input editor. The tool handles any well-formed XML document, including those with namespaces, CDATA sections, and processing instructions.
2. •Choose the indentation style: 2 spaces, 4 spaces, or tabs.
3. •View the formatted output with proper indentation and syntax highlighting that makes the element hierarchy clear.
4. •Check validation results. If the XML is malformed (e.g., unclosed tags, mismatched tag names), you will see an error message describing the problem and its location.
5. •Copy the formatted XML for use in your configuration files, API requests, or documentation.

What is XML?

XML (eXtensible Markup Language) is a markup language defined by the W3C for encoding documents in a format that is both human-readable and machine-readable. Unlike HTML, which has a fixed set of tags, XML allows users to define their own tags, making it a flexible format for representing structured data.

An XML document consists of elements (defined by start and end tags), attributes (name-value pairs on start tags), text content, and special constructs like CDATA sections (which contain unescaped text), comments, and processing instructions. Every XML document must have exactly one root element that contains all other elements.

XML is stricter than HTML about syntax. Every start tag must have a matching end tag (or be self-closing), tag names are case-sensitive (<Item> and <item> are different elements), attribute values must be quoted, and special characters must be escaped using entities (& for &, < for <, > for >, " for ", ' for ').

XML namespaces allow elements and attributes from different vocabularies to coexist in the same document without naming conflicts. A namespace is declared with an xmlns attribute and associated with a URI prefix. This is essential in formats like SOAP, SVG, and XHTML.

While JSON has replaced XML for many web API use cases, XML remains dominant in enterprise systems (SOAP web services), configuration files (Maven's pom.xml, .NET config files, Android layouts), document formats (DOCX, SVG, RSS/Atom feeds), and industries with established XML-based standards (healthcare with HL7, finance with FIX/FIXML).

Common use cases

• •Configuration file maintenance: Many frameworks and tools use XML configuration files (Maven, Spring, Android). Formatting makes them readable and helps spot structural errors.
• •SOAP API debugging: SOAP messages are XML-based. Formatting raw SOAP requests and responses reveals the message structure and helps identify problems.
• •RSS/Atom feed debugging: RSS and Atom feeds are XML documents. Formatting helps verify feed structure and identify malformed entries.
• •Data interchange validation: When exchanging XML data between systems, formatting and validating the XML before transmission catches errors early.

FAQ

What is the difference between well-formed XML and valid XML? Well-formed XML follows basic syntax rules (proper nesting, matched tags, quoted attributes). Valid XML additionally conforms to a schema (DTD or XSD) that defines which elements and attributes are allowed and their structure. This tool checks for well-formedness.

Why does my XML have namespace prefixes? Namespace prefixes (like xs: in <xs:element>) associate elements with a namespace URI, allowing elements from different schemas to coexist. The prefix itself is arbitrary; what matters is the URI it maps to.

Can XML have comments? Yes. XML comments use the syntax <!-- comment text -->. Comments can appear anywhere in the document except inside tags or other comments. The formatter preserves comments in the output.

Is my data safe?

Yes. This tool runs entirely in your browser. Your data is never sent to our servers. XML parsing, validation, and formatting are all performed locally using your browser's built-in DOMParser API and JavaScript formatting logic.