Welcome to the world of Wireless Markup Language (WML)! If you’ve ever heard of HTML for building websites, you’re already on the right track. WML is a markup language just like HTML, but it was specifically designed for the unique challenges of early mobile devices and their slow, low-bandwidth connections. Imagine trying to load a modern website over a dial-up connection on a screen the size of a credit card; WML was engineered to make that experience fast and functional. It’s an application of XML, which means it follows a strict set of rules for its structure.

The single most important concept to grasp in WML is the “Deck and Cards” metaphor. Unlike an HTML document, which is considered a single “page,” a WML file is structured as a “deck.” This deck can contain multiple “cards,” where each card represents a single screen of information for the user. This structure is the key to understanding how WML works and why it was so efficient for older mobile phones.