What is XML (eXtensible Markup Language)?

What is XML?

XML (eXtensible Markup Language) is a text-based format that describes data with opening and closing tags. HTML marks up the document structure a browser renders; XML marks up what the data means and how it is organized, such as invoice, customer, and amount fields in a billing document.

How Does XML Work?

An XML document has one root element, with nested elements, attributes, and text values underneath it. Applications read the document through a parser and can validate it against an XSD or DTD schema. Namespaces help prevent collisions when different systems use the same field names for different meanings.

XML is readable by humans, but in business systems it is usually processed automatically. JSON is shorter and more common in modern web APIs, while XML remains useful when strict schemas, digital signatures, and document-style exchange are required.

Common Uses

• SOAP services: SOAP messages are carried inside XML envelopes.
• Enterprise integrations: Banking, insurance, public-sector, and logistics systems may require XML schemas.
• Document formats: Office Open XML, SVG, RSS, and Atom are built on XML-style structures.
• Archiving and compliance: Explicit field definitions help when structured records must be stored for years.

Business Use

XML often appears in legacy ERP links, payment and insurance services, e-document flows, and government integrations. A new web application may prefer JSON, but if the counterparty expects XML, schema validation, character encoding, and error-response mapping become central to a reliable integration.

Parser configuration matters as well. Features such as external entity resolution should be disabled unless explicitly needed, and size limits should be enforced for large or deeply nested documents.