XML formatter & validator

Format, minify, and validate XML documents. Shows parsing errors with details.

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What is XML?

XML (Extensible Markup Language) is a markup language designed to store and transport structured data in a format that's both human-readable and machine-parseable. Unlike HTML, XML has no predefined tags — you define your own elements and attributes to match your data model. This flexibility made XML the universal data interchange format of the early 2000s.

XML is self-describing: element names convey meaning (<price currency="USD">29.99</price>), and the tree structure naturally represents hierarchical data. It supports namespaces for avoiding naming conflicts, schemas (XSD) for formal validation, and XSLT for transforming documents between formats.

XML vs JSON

JSON won the web API battle for good reasons: it's lighter (no closing tags), maps directly to JavaScript objects, and is simpler to parse. Most modern REST APIs return JSON by default, and frontend frameworks consume it natively.

But XML still dominates several domains. SOAP web services — the backbone of enterprise integration in banking, healthcare, and government — use XML exclusively. RSS and Atom feeds are XML. SVG graphics are XML. Android layout files, Maven build configurations, and .NET project files are all XML-based.

XML also has capabilities JSON lacks: namespaces prevent element name collisions when combining documents from different sources, schemas (XSD) provide formal type validation, XSLT enables document transformation, and XPath provides a powerful query language for navigating document trees.

The practical advice: use JSON for web APIs and JavaScript-centric applications, use XML when your ecosystem requires it or when you need its advanced features.

Frequently asked questions

How does XML validation work in this tool?
This tool uses the browser's built-in DOMParser API to parse your XML. If the XML is malformed — missing closing tags, improperly nested elements, invalid characters — the parser generates a <parsererror> element with details about what went wrong. This is well-formedness checking (valid XML syntax), not schema validation (checking against an XSD or DTD). For schema validation, you'll need a dedicated XML validation tool or library.
Is XML still relevant in modern development?
Yes, though its role has changed. JSON has replaced XML as the default data interchange format for web APIs, but XML remains essential in many domains. SOAP web services (common in enterprise and financial systems), RSS and Atom feeds, SVG graphics, XHTML, Android layout files, Maven/Gradle build configurations, .NET config files, and Microsoft Office documents (which are ZIP archives containing XML) all rely on XML. If you work in enterprise software, healthcare (HL7), or publishing (EPUB), you'll encounter XML regularly.

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