GuideML (Guide Markup Language) is a

document markup language Markup language refers to a text-encoding system consisting of a set of symbols inserted in a text document to control its structure, formatting, or the relationship between its parts. Markup is often used to control the display of the document ...

. GuideML is an application of

XML Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. T ...

standards. It consists of a safe subset of

XHTML Extensible HyperText Markup Language (XHTML) is part of the family of XML markup languages. It mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which Web pages are formulated. While HTML, prior ...

with added tags for specific features of the software. The objective is to provide something that resembles HTML but is simpler to learn, and allows basic textual content to be formatted in a skinnable way. Early versions of the

h2g2 The h2g2 website is a British-based collaborative online encyclopedia project. It describes itself as "an unconventional guide to life, the universe, and everything", in the spirit of the fictional publication '' The Hitchhiker's Guide to ...

software offered full HTML markup as an option, but this was removed for security reasons; thus only parts of HTML which are considered to exist in GuideML can now be used, with things such as

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of websites use JavaScript on the client side for webpage behavior, of ...

and externally hosted images being removed by the parser.

See also