Cascading Stylesheet

In short

Declarative styles for the Web.

item info
types Markup, Text (plain)
preferred ⚠️ under conditions
extensions .css
related formats CSV, HTML, JavaScript, JSON, JSX, Markdown, SGML, SQL, TeX, Text, XHTML, XML, XSLT, YAML
wikipedia Cascading_Style_Sheets


Cascading Style Sheets is a language for styling HTML documents. It is widely used on the web.

HTML files may contain CSS styles inside, or they may refer to other files for their styling.


The World-wide-web is one of the most dynamic corners of IT. Standards are always on the move, and new patterns of organizing web content replace the best practices of yesterday.

CSS has gone through several major versions.

The format is Text, so CSS files are easy to open, but the meaning of the styles is dependent on the version of the CSS styling engine that has been used.

Moreover, in real-world web applications, CSS files are often deliberately uglified, in order to decrease their file size.


For archiving it must be made clear to which files the CSS files refer and which version of CSS is being used. As browser-specific extensions may exist, the target environment of the files must be known, unless only basic elements have been used. If the CSS files contain links to other CSS files or external files, these links must be working.

If the CSS files have been uglified, their non-uglified sources should be archived as well.

See also