ARML (augmented reality markup language) is a specification that allows content developers create content that is displayed on various mobile AR browsers. Wikitude 4 is the first browser that natively supports ARML. ARML is built on a subset of KML, a set of common tags supported across all browsers and some browser (e.g. Wikitude) specific extensions. This specification describes the full set of tags supported by Wikitude 4. The ARML document must be a valid XML in UTF-8 encoding. The text of the tags may be enclosed by a CDATA section to prevent un-escaped characters like <, >, ...