What Is XML? Explained Simply

What XML is

XML stands for eXtensible Markup Language, and it is a format for storing and sharing structured data in a way that both humans and machines can read. Like HTML, it uses tags to label information, but while HTML has a fixed set of tags for describing web pages, XML lets you define your own tags to describe whatever kind of data you need. This flexibility is why it is called 'extensible,' and it is what made XML a widely used format for exchanging data.

How it works

XML organizes data using custom tags that you create to describe the content. Information is nested in a tree-like structure, with elements containing other elements, much like folders containing files. For example, a 'book' element might contain 'title,' 'author,' and 'year' elements. This structure is self-describing: the tags tell you what each piece of data means. Because it is just structured text, XML can be read by people and processed by virtually any programming language.

Why structure matters

The value of XML is that it gives data a clear, agreed-upon structure that different programs can understand. If two systems need to exchange information, say, an online store and a shipping company, they can agree on an XML format, and each can reliably read what the other sends. This made XML popular for data exchange, configuration files, and document formats, anywhere a precise, shareable structure for data was needed across different systems and tools.

XML vs. JSON

XML is often compared to JSON, a newer data format. JSON is more compact and has become the default for many web APIs, especially those used by JavaScript. XML is more verbose but offers features JSON lacks, such as attributes, comments, and powerful validation and querying tools. Neither is simply better; they suit different needs. Many newer systems favor JSON for its simplicity, while XML remains common where its extra structure and tooling are valuable.

Where XML is used

Despite JSON's rise, XML is still widely used. Many configuration files, document formats (including modern office documents under the hood), and enterprise systems rely on it. RSS feeds, which syndicate content from websites, are XML-based. Numerous industry data standards are defined in XML. Its maturity, flexibility, and strong tooling mean XML continues to play an important role, even as newer formats have taken over in some areas like web APIs.

Why it matters

XML is a foundational data format that shaped how structured information is stored and exchanged across the digital world. Understanding it, and how it compares to alternatives like JSON, clarifies a key part of how different systems share data. Whether you encounter XML in configuration files, document formats, or data feeds, knowing what it is and how its tag-based structure works makes a common and important technology much less mysterious.

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See also: What is JSON? Explained simply, What is HTML? Explained simply.

Sources

• XML - Wikipedia

Published date reflects the original event date (2024-09-24). This article is original Skillo editorial written from the sources above; facts were verified in September 2026.