XML Viewer & Formatter

XML (Extensible Markup Language) is a W3C-standardized markup language designed for storing and transporting structured data in a platform-independent, self-descriptive format. Unlike HTML — which instructs browsers on how to display information — XML is purely about data: its structure, its relationships, and its meaning. This distinction has made XML the backbone of industry standards that require rigorous, machine-verifiable data exchange: XRechnung and ZUGFeRD in German e-invoicing, SOAP web services, OpenDocument (ODF), RSS and Atom feeds, SVG vector graphics, Maven build files, and the Office Open XML format used by Microsoft Word and Excel.

Every XML document is built from a hierarchy of elements enclosed in matched start and end tags (e.g., <Invoice>...</Invoice>). Elements can carry attributes directly within their opening tag, contain text content, hold nested child elements, or mix both. Well-formed XML must satisfy a strict set of rules: every opened tag must be closed, tags must be properly nested without overlapping, the document must have exactly one root element, attribute values must be quoted, and certain characters (<, >, &, ", ') must be escaped as XML entities. Beyond well-formedness, valid XML additionally conforms to a schema — either a DTD (Document Type Definition) or an XSD (XML Schema Definition) — which specifies exactly which elements and attributes are permitted, their data types, and their cardinality. This two-level discipline is what allows XRechnung invoices to be machine-processed reliably across dozens of different ERP systems and government portals.

In the German and EU e-invoicing landscape, XML is central to legal compliance. The XRechnung standard — mandated for invoices to federal authorities since 2020 and extended to state authorities across all German Bundesländer — is based on two XML syntaxes: UBL 2.1 (OASIS Universal Business Language) and UN/CEFACT CII (Cross-Industry Invoice). ZUGFeRD embeds CII XML as an attachment inside a PDF/A-3 document. The European EN 16931 core invoice standard underpins both, defining a set of semantic business terms (BT-1 for invoice number, BT-9 for payment due date, etc.) that are mapped to XML element paths in each syntax. Knowing how to read and navigate these XML files — using the namespace prefixes cbc: (Common Basic Components) and cac: (Common Aggregate Components) in UBL — is essential for accountants, ERP developers, and tax auditors working with public procurement systems in Germany.

Our XML Viewer is designed for developers, accountants, and IT professionals who need to quickly inspect XML documents without installing a dedicated editor.

1. Paste or Upload — Paste your XML content directly into the input field, or click "Upload File" to select an XML file from your device. The tool accepts any well-formed XML regardless of the document type — XRechnung invoices, SVG graphics, Maven pom.xml, SOAP responses, or custom XML formats.
2. Parse & Format — Click the "Parse & Format XML" button or press Ctrl+Enter. The tool validates your XML syntax for well-formedness and, if valid, builds an interactive tree view and a cleanly indented formatted output. If your XML contains a syntax error, the tool reports the exact position of the problem.
3. Explore the Tree — Navigate the collapsible tree view to inspect element names, attributes, and text content. Click the chevron icons to expand or collapse nested sections. This is especially useful for large XRechnung invoices where you want to jump directly to the SellerParty, LineItem, or TaxTotal section without scrolling through hundreds of lines.
4. Copy Formatted Output — Use the "Copy formatted" button to copy the cleaned, properly indented XML to your clipboard, ready to paste into a code editor, email, or documentation system.

All processing happens entirely in your browser using the fast-xml-parser JavaScript library. Your XML data never leaves your device, is never uploaded to a server, and is never stored anywhere. This makes the tool fully GDPR-compliant for processing sensitive business documents. Free users can process files up to 500 KB; Pro users have no size limit.

When you click "Parse & Format XML", the browser passes your XML string to fast-xml-parser — a high-performance JavaScript library that runs entirely client-side. The parser first checks well-formedness: are all tags properly nested? Does the document have a single root element? Are all attribute values quoted? Are all reserved characters (<, >, &, ", ') correctly escaped? If any rule is violated, parsing stops and the error position is reported.

If the XML is well-formed, fast-xml-parser converts it into a JavaScript object tree. Our rendering layer recursively traverses this object and builds a React component tree where each XML element is rendered as a collapsible node with its tag name, attributes, and child elements. Namespace prefixes (cbc:, cac: in XRechnung UBL; rsm:, ram:, udt: in CII) are preserved exactly as they appear in the source — no namespace resolution that might obscure the original structure.

The formatted output is produced by a separate serialization pass: the parsed object tree is serialized back to XML text with consistent 2-space indentation at each nesting level, normalized attribute quoting, and CDATA sections preserved intact. This produces the clean, properly formatted XML that code editors like VS Code or IntelliJ IDEA would display with their auto-format function — without requiring you to install or open an editor.