MIME Type to Extension Lookup

About this calculator

A MIME type (Multipurpose Internet Mail Extensions, formally an “Internet media type” under IANA's registry) is the type/subtype string — like image/png, application/pdf or text/csv — that HTTP responses, email attachments and file uploads use in the Content-Type header to tell a client how to interpret a payload, independent of the filename. This tool looks up the conventional file extension for a given MIME type, or the reverse, using IANA's registered media types and the common mappings browsers and web servers rely on.

Web developers configuring file upload validation, server administrators setting Apache or Nginx MIME type mappings, and API developers handling multipart form data all need this correspondence — a mismatch between the declared MIME type and the actual file extension is a classic source of broken downloads, rejected uploads, or security issues, since some browsers sniff content type differently than the server declares it, and validating both together closes that gap.