What is .css?
.css files contain Cascading Style Sheets, a language used to describe the presentation of a document written in a markup language like HTML. CSS handles the look and feel—layout, colors, fonts, and responsiveness—separating content from design.
This quick guide explains when to use .css files, how to open them on any device, and how to share them instantly with FileXhost.
When to use .css files
- You want to style HTML web pages.
- You need to create responsive designs that work on mobile and desktop.
- You want to apply consistent branding across a website.
- You are separating content (HTML) from presentation (CSS) for better maintainability.
How to open .css files
CSS files are plain text and can be opened in any text editor like VS Code, Sublime Text, or Notepad. Web browsers also read and apply them automatically when linked in an HTML file.
Algorithm details
CSS is a declarative language consisting of rulesets. Each rule selects elements and applies property-value pairs. Browsers parse CSS to construct the CSSOM (CSS Object Model) and combine it with the DOM to render the page.
Browser & platform support
- Desktop: Supported natively by 100% of web browsers.
- Mobile: Supported natively by all mobile browsers.
- OS: Viewable as text on any OS.
Format comparison
| Feature | Details |
|---|---|
| Purpose | Solely for presentation and layout, unlike HTML (structure) or JS (behavior). |
| Readability | Human-readable text format, though often minified for production. |
| Capabilities | Controls visual aspects: color, layout (Flexbox/Grid), animation, and typography. |
How to create css files
- Code Editors: VS Code, Sublime Text, Atom.
- Browser DevTools: Inspect > Styles (can save changes).
- Preprocessors: SASS/SCSS compilers.
How to convert css files
- Minifiers: CSSNano, CleanCSS (to reduce size).
- Preprocessors: SASS/LESS to CSS.
- FileXhost: Upload to host and link in your projects.
Advantages & disadvantages
Advantages
- Separates design from content
- Enables responsive web design
- Reusable across multiple pages
- Cached by browsers for performance
Disadvantages
- Global scope can lead to conflicts (specificity wars)
- Different browsers may render styles slightly differently
- Large files can block rendering (render-blocking resource)
Tools & software
Editors
VS Code, Sublime Text, WebStorm
Browsers
Chrome DevTools, Firefox Developer Edition
Processors
PostCSS, SASS, Tailwind CSS
Frequently asked questions
What is the difference between CSS and HTML?
HTML provides the structure and content of the page, while CSS provides the visual style and layout.
Can CSS contain viruses?
Generally no, as CSS is not executable code. However, it can be used for clickjacking or data exfiltration attacks in rare cases, so always sanitize user input.
What is minified CSS?
Minified CSS has all whitespace and comments removed to reduce file size and improve load times.
Technical specs
- File type
- Code
- Extension
- .css
- MIME type
- text/css
- Compression
- Uncompressed
- Max file size on FileXhost
- Up to 25 MB per file on the free plan and up to 1 GB on Pro FileXhost accounts.
Share .css files instantly
Upload your .css file to FileXhost to get a clean, shareable URL in seconds. View the file in a modern browser, protect access with optional settings, and let others download it without any confusing ads or cluttered file pages.
Upload .css file