MIME type

A MIME type (Multipurpose Internet Mail Extensions, now formally just “media type” per RFC 6838) is a two-part identifier in the format type/subtype that tells a client what kind of data it’s looking at.

Common examples:

• text/html — HTML document
• application/json — JSON data
• image/png, image/jpeg, image/webp — image formats
• application/pdf — PDF document
• multipart/form-data — file upload payload
• application/octet-stream — opaque binary; the “just bytes, you figure out what it is” fallback

HTTP responses carry MIME types in the Content-Type header. Data URIs (used by our image-to-Base64 tool) embed the MIME type directly: data:image/png;base64,iVBOR.... Browsers use the declared MIME type to decide how to render or download a resource.

Historical note: MIME was originally defined for email attachments. The same registry now defines media types for the web, IM, RSS, and most modern protocols.