MIME Type Lookup content-type

What this tool does

A MIME type is a standard string describing a data format, written as type/subtype, such as text/html, application/json, or image/png. On the web it travels in the HTTP Content-Type header, and browsers use it to decide how to handle what they receive.

Getting Content-Type wrong causes a range of problems. A JSON response labelled text/plain may not be parsed by client libraries, an image with the wrong type will not display, and a file meant to be downloaded may open inline instead, or the reverse.

MIME types matter for uploads too, although the type reported by the client can be forged, so the server must inspect the actual file contents.

When to use it

Use it when setting the Content-Type header for a download response, when defining a list of accepted upload formats, when adding a type mapping to web server configuration, or when investigating why a file returned by an API is handled incorrectly by browsers.

Input and output examples

Notes and limitations

Checking the MIME type of an upload is not a security control. The Content-Type sent by a client is arbitrary, so an executable can be presented as an image. Servers should verify the real file signature and prevent script execution in upload directories. Note also that some formats have more than one type in circulation; JavaScript has been served as both text/javascript and application/javascript, with text/javascript now standard.

Frequently asked questions