---
title: ".css file — what it is and how to open it"
description: "A .css file is a Cascading Style Sheet. The text file that tells a web page how to look. How to open one on Windows, macOS and Linux, and what to convert it to."
url: https://atoneplace.net/file/css/
site: "At One Place"
---

# .css files

**.css file: Cascading Style Sheet**

The text file that tells a web page how to look.

## What opens a .css file

- **Windows:** Visual Studio Code, Notepad (built in), Any web browser (shows source)
- **macOS:** Visual Studio Code, TextEdit (built in), Any web browser (shows source)
- **Linux:** Visual Studio Code, Text Editor (built in)
- **In a browser:** CodePen, CodeSandbox

## What a .css file is

CSS holds the rules — colours, fonts, spacing, layout — applied to HTML elements, and is a W3C standard. It is plain text you can read and edit in anything, and it does nothing on its own: opening a .css file in a browser shows the source, not a page. Sites often ship a minified version with all whitespace stripped, which is valid but painful to read.

## Converting it

A .css file is commonly converted to .scss, .less or .txt. It is a plain text format, so any text editor can open and edit it directly.

## Details

- **Extension:** .css
- **Full name:** Cascading Style Sheet
- **Category:** Code and scripts
- **MIME type:** text/css
- **Created by:** W3C
- **Format:** Plain text

## Common questions

### How do I open a .css file?

On Windows use Visual Studio Code; on macOS use Visual Studio Code; on Linux use Visual Studio Code. The text file that tells a web page how to look.

### What is a .css file?

Cascading Style Sheet. CSS holds the rules — colours, fonts, spacing, layout — applied to HTML elements, and is a W3C standard. It is plain text you can read and edit in anything, and it does nothing on its own: opening a .css file in a browser shows the source, not a page.

### Can I convert a .css file?

Yes. It is usually converted to .scss, .less or .txt, either by exporting from one of the programs listed above or with a format converter.

## Related pages

- [.html — HyperText Markup Language](https://atoneplace.net/file/html/)
- [.js — JavaScript Source](https://atoneplace.net/file/js/)
- [.py — Python Source](https://atoneplace.net/file/py/)
- [.java — Java Source](https://atoneplace.net/file/java/)
- [.tsx — TypeScript Source (JSX)](https://atoneplace.net/file/tsx/)
- [.cpp — C++ Source](https://atoneplace.net/file/cpp/)
- [.php — PHP Source](https://atoneplace.net/file/php/)
- [.c — C Source](https://atoneplace.net/file/c/)
- [.cs — C# Source](https://atoneplace.net/file/cs/)
- [.go — Go Source](https://atoneplace.net/file/go/)
- [.rs — Rust Source](https://atoneplace.net/file/rs/)
- [.rb — Ruby Source](https://atoneplace.net/file/rb/)

## Sources

- Media Types Registry — IANA (https://www.iana.org/assignments/media-types/)
- Official vendor product documentation — At One Place (/about/)