HTML (HyperText Markup Language) is a markup language used to create the structure and content of a page or web application. The structure of the website or application is built using blocks (tags), passing properties to them using attributes and nesting them in the appropriate way. HTML also provides an API which can be handled with Javascript. In HTML 5, native multimedia support has been improved by adding new elements such as video, audio, canvas, support for SVG and MathML, which has also been added. New elements related to semantics on websites have been added, such as: main, section, article, header, footer, aside, nav and figure, thanks to which indexing robots can better deal with the identification of text on the page (better SEO). A number of improvements have been made to the existing elements. HTML5 also better defines the processing of invalid documents.

Some of the new APIs included in the W3C or WHATWG specification:

• Canvas - allows for dynamic, script rendering of shapes and bitmap images;
• Timed Media Playback - video/audio API;
• Editable content;
• Drag and drop;
• History;
• Web Storage - a value storage structure that provides behaviour similar to cookies, but with greater capacity and an improved API;
• Geolocation;
• File - API designed to handle file sending and file manipulation;
• Web Audio - a high-level JavaScript API for processing and synthesizing audio in web applications;
• ClassList;
• WebRTC - streaming and multimedia data transmission;