What is the MIME type of .css files?
The MIME type (media type) for Cascading Style Sheets files with the .css extension is text/css. Browsers refuse to apply a stylesheet served with the wrong type when X-Content-Type-Options: nosniff is set — a frequent cause of “unstyled page” bugs on misconfigured servers and S3 buckets.
Content-Type header
Content-Type: text/css; charset=utf-8Text-based types should include a charset so the browser decodes characters correctly.
Server configuration
| Server | Configuration |
|---|---|
Nginx (mime.types or types {}) | text/css css; |
Apache (.htaccess) | AddType text/css .css |
IIS (web.config) | <mimeMap fileExtension=".css" mimeType="text/css" /> |
| Node.js / Express | res.type('css') or res.setHeader('Content-Type', 'text/css; charset=utf-8') |
| Amazon S3 | Set Content-Type: text/css on the object (metadata), or pass --content-type text/css to aws s3 cp |
Should .css files be compressed?
Yes. Cascading Style Sheets is text, so enabling gzip or Brotli for text/css typically saves 50–80 % of the transfer size. Make sure your server’s compression list includes this type — check with the website compression test.
Why the MIME type matters
Browsers decide what to do with a response — render, run, play or download — from the Content-Type header, not the file extension. With X-Content-Type-Options: nosniff, a wrong type causes stylesheets and scripts to be blocked outright. For uploads, never trust the type sent by the client; check the file’s content (its magic bytes) on the server.
Frequently asked questions
What is the MIME type for .css?
text/css.How do I set the Content-Type for .css in Nginx?
text/css css; is listed in the types block (usually in /etc/nginx/mime.types) and reload Nginx.