The MIME type text/vnd.wap.wml is used to indicate the encoding required for the WML file type. This MIME type falls under the category "text".

WML stands for Wireless Markup language. It is a markup language based on XML and is intended for use with Wireless Access Protocol implementing devices. The main devices that implement WAP are mobile phones and WML preceded all other markup languages that are now supported by these devices. Since the modern mobile phones have higher processing power, more memory and greater bandwidth available to them, full support for markup languages like HTML and XML are becoming more commonplace.

WML was built using three existing markup languages of that time. These were HDML (Handheld Device Markup Language) by Openwave, Tagged Text Markup Language (TTML) by Nokia and a proprietary markup language made for Ericsson handheld devices. It was built by the WAP forum and the first standard version was WML 1.1 that was released in 1998. In 2001, it was followed by the specification of WML 2.0, which has not been widely adopted yet. WML 2.0 was intended to bring WML and XHTML basic closer and to be the markup language for WAP 2.0.