Overview

Wireless Markup Language (WML) is an XML-based markup language designed to create user interfaces for early mobile phones and other constrained wireless devices that used the Wireless Application Protocol (WAP). WML was intended to present small-screen, low-bandwidth content to devices with limited processing power and simple input methods. Unlike traditional HTML, WML enforces strict XML rules, so every element must be well-formed, nested, and closed.

Structure and characteristics

The basic unit of WML content is the "deck," which contains one or more "cards." A deck groups related screens together and a card represents a single display or interaction. Typical elements include <wml> (root), <card>, <p> for text, <do> for actions, and <anchor> for links. Navigation is frequently handled with <go> actions and event blocks. Because WML follows XML, correct syntax is important: tags must be properly nested and every open tag must have a matching close tag.

  • Cards and decks: modular presentation suited for small screens.
  • WMLScript: a lightweight scripting language used for client-side logic and simple calculations.
  • Server and gateway role: WML content was typically delivered through WAP gateways that adapted HTTP for WAP transports.
  • MIME and delivery: WML files were commonly served with the MIME type text/vnd.wap.wml.

History and development

WML emerged in the late 1990s as part of the WAP initiative to enable web-style services on mobile handsets. Early mobile browsers, often called microbrowsers or WAP browsers, implemented WML to present menus, message prompts and simple forms. Over time WAP 1.x and WML were superseded by WAP 2.0 and then by broader web standards adapted for mobile, such as XHTML Mobile Profile and, later, responsive HTML5. For historical and technical context see the technical overview and the WAP device descriptions.

Uses, examples and decline

Typical WML applications included operator portals, simple banking menus, news headlines and weather briefings optimized for low bandwidth. A minimal WML deck might contain several cards with text and navigation commands. As modern smartphones adopted full-featured browsers and higher bandwidth, developers migrated away from WML toward standards that support richer layout, multimedia, and CSS. For a comparison with legacy and modern formats see WML vs HTML and XML-based mobile profiles.

Practical distinctions and notable facts

WML should be seen as a product of its era: it solved the problem of constrained devices and networks but required different authoring and deployment practices than desktop HTML pages. Key distinctions are strict XML syntax, card-based navigation, and reliance on a WAP-capable browser or gateway. For developer guidance and sample syntax consult syntax notes, example archives at example repositories, and historical specification material at standards resources.

Although WML is rarely used today, understanding its design helps explain early mobile web constraints and why later mobile web standards emphasized compatibility with desktop HTML while adding device-adaptive features.