MIME Type Reference

MIME types tell browsers and servers what kind of content they are handling. When a web server sends a file, it includes the MIME type in the Content-Type header so the browser knows how to display or process it.

This database covers the most common MIME types. For less common types, you can refer to the IANA (Internet Assigned Numbers Authority) official registry which maintains the complete list.

Some file extensions can map to multiple MIME types depending on context. For example, .js can be application/javascript or text/javascript. This tool shows the most commonly used mapping.

type/subtype plus optional parameters, standardized by RFC 6838: text/html; charset=utf-8, or multipart/form-data; boundary=----WebKitFormBoundary. The type is the broad category - application, audio, font, image, text, video, among the IANA-registered trees - and parameters carry details like charset or the multipart boundary.

It is the fallback: unknown binary data. Servers send it when the type is unknown or when forcing a download, and clients respond by saving the file rather than opening it. Receiving octet-stream for a document you expected to render usually means a missing or wrong mapping server-side.

Browsers inspect the first bytes of a response to guess its actual type when Content-Type is missing or generic - and whether a payload is treated as HTML or script has security implications, so the algorithm is specified. A server sends X-Content-Type-Options: nosniff to insist the declared type be obeyed, which stops, for example, a JSON reply from being rendered as HTML.

text/html and text/css for pages and styles; text/javascript (the current standardized value for scripts) ; application/json for APIs; multipart/form-data for file uploads; image/svg+xml for scalable graphics; and application/wasm for WebAssembly module responses. Getting these right affects execution mode, security, and CORS handling.

They are containers packing several parts of different types into one message, each part with its own headers and a boundary delimiter. multipart/form-data carries form file uploads in HTTP; multipart/alternative lets email offer the same content as plain text and HTML; multipart/byteranges powers resumable downloads over HTTP Range requests.