MIME-Types

The Multipurpose Internet Mail Extensions, known also as MIME type, is a specification extending the format of email to support sending images, audio/video files, archives, etc. The specification is standardized in IETF RFC 6838.

Browsers generally use the MIME type (and not the file extension) to determine how to process a document; that’s why it is important to set up servers correctly for attaching a proper MIME type to the response object's header. If it is not configured correctly, browsers may misinterpret the files' contents, and sites won't work correctly. Downloaded files may be mishandled as well.

Syntax

Type/Subtype

The structure of MIME-type consists of a type and subtype, separated by a slash (/), without spaces. MIME-type is not case-sensitive, but it is commonly written in lower case.

A MIME type must always have both a type and subtype. Each type has its set of possible subtypes.

To provide additional details, you can use an optional parameter.

type/subtype;parameter=value

MIME-types are divided into two types: discrete and multipart. Each of them has specific subtypes.

Discrete Types

text/plain
text/html
image/jpeg
image/png
audio/mpeg
audio/ogg
audio/*
video/mp4
application/*
application/json
application/javascript
application/ecmascript
application/octet-stream
…

Discrete type indicates the category of the document, it can be one of the following:

For describing a text document, that doesn’t belong to a particular subtype, text/plain is used. Documents containing binary data without a specific subtype are described using application/octet-stream.

Multipart Types

multipart/form-data
multipart/byteranges

Multipart types indicate a category of the document, which consists of several parts, and each one can belong to different MIME-types.

Table of MIME-Types