MIME Types

MIME types are how servers tell browsers what kind of file they're sending. The browser uses this information to decide what to do with it — render it inline, hand it to a plugin, or prompt a download. The format is always type/subtype: text/html, image/png, application/json. The broad type (text, image, audio, video, application) gives the general category; the subtype is the specific format. Search by either the extension or the MIME string here and you'll get the match and any common alternatives.

The one that causes the most confusion is application/octet-stream

This is the generic binary MIME type — essentially "I don't know what this is, treat it as raw bytes." Browsers respond to it by offering a download dialogue, which is sometimes intentional (you want the user to download a file) and sometimes a mistake (you served a PDF but forgot to set application/pdf so the browser downloaded it instead of displaying it). If you're building a file download endpoint and you want the browser to always download regardless of format, application/octet-stream is the correct type. If you want the browser to decide how to handle it based on what it is, set the actual content type. The other common source of confusion is font files — font/woff2 is now the correct type for WOFF2, but older configs use application/font-woff2. Modern browsers accept both, but newer servers should use the font/ namespace. Look up any extension here to see the current canonical type and any legacy aliases.