Different features of ExT are defined in different libraries. When writing a document, one or more of these libraries can be imported depending on what features are required in the document. These libraries define how to render those ExT constructs in HTML:
LibDoc provides basic document features like bold and italic text, multiple levels of sections, ordered and unordered lists, images, and hyperlinks.
LibCite provides support for citations, and generation of bibliography.
LibSVG allows the user to add Support Vector Graphics to documents. It is useful for creating flags for countries and cities.
LibInfobox helps the user to create Infoboxes which contain basic information about a country or city like flag, population, area, country code, and others.
LibTOC extends all the libraries mentioned above and adds a new command to generate a table of contents and prefix it to its contents.
There are some libraries which do not define new ExT commands but define functions which are used in other libraries or documents written as CP programs:
LibArray defines functions for arrays like subarray, head, and tail
LibNum defines functions for basic operations on numbers like converting them from Double to Int, and converting a large Int to String of format "xxx million"
Some libraries just store information that can be used in documents:
database stores basic information about different cities and countries. This information can be used in different documents like creating Infoboxes, or creating a sorted list of smallest countries.
refs stores a list of dummy references which are used to demonstrate how citations and bibliographies work.
These libraries combine traits defined across different libraries into a single trait for easier usability when writing documents:
LibCity combines different libraries (LibTOC, database, and refs) that are used in creating pages for cities into a single library.
LibState performs the same function as LibCity but for countries.