text/css
textThe MIME type for CSS stylesheets. Browsers require stylesheets linked via <link rel='stylesheet'> to be served as text/css or they are blocked. RFC 2318 defines this type. Missing or incorrect Content-Type on CSS files is a common cause of broken styling in strict-mode browsers and Content Security Policy environments.
Details
text/css is defined by RFC 2318 and is required for browser stylesheet loading.
Browser enforcement: browsers will refuse to apply stylesheets served with the wrong MIME type. This is a security measure to prevent CSS injection via JSON or other responses incorrectly loaded as stylesheets.
Server configuration: ensure your web server maps .css → text/css. Common issue: nginx defaults not updated, serving CSS as application/octet-stream.
CSP interaction: if a Content-Security-Policy style-src directive is present, the stylesheet must also match that policy regardless of MIME type.
Common use
CSS stylesheets served to browsers
Security note
Never serve dynamic content (user data) as text/css. CSS can be used for data exfiltration via attribute selectors.