MIME Types: What They Are and How to Use Them

What Is a MIME Type?

A MIME type (Multipurpose Internet Mail Extensions type, also called Media Type or Content Type) is a label that identifies the format of data. Originally created for email attachments, MIME types are now used everywhere data format identification is needed — HTTP responses, file uploads, data URLs, and HTML.

MIME Type Syntax

MIME types follow this format:

type/subtype
type/subtype; parameter=value

Examples:

• text/html — HTML document
• text/html; charset=UTF-8 — HTML with encoding parameter
• application/json — JSON data
• image/png — PNG image
• multipart/form-data; boundary=something — Form data with boundary

MIME Type Categories

text

Human-readable text content:

• text/plain — Plain text
• text/html — HTML markup
• text/css — CSS stylesheets
• text/javascript — JavaScript (though application/javascript is more accurate)
• text/csv — CSV data

image

Visual content:

• image/jpeg — JPEG photos
• image/png — PNG with transparency
• image/gif — Animated GIFs
• image/webp — Modern efficient format
• image/svg+xml — SVG vector graphics
• image/avif — AV1 Image File Format (modern, high efficiency)

audio

Sound content:

• audio/mpeg — MP3 audio
• audio/ogg — Ogg Vorbis
• audio/wav — Uncompressed audio
• audio/aac — AAC audio
• audio/webm — WebM audio

video

Video content:

• video/mp4 — MP4 video
• video/webm — WebM video
• video/ogg — Ogg Theora

application

Non-text binary or structured data:

• application/json — JSON data
• application/xml — XML data
• application/pdf — PDF documents
• application/zip — ZIP archives
• application/gzip — Gzip compressed
• application/octet-stream — Unknown binary (generic binary)
• application/x-www-form-urlencoded — HTML form data

multipart

Composite content with multiple parts:

• multipart/form-data — File upload forms
• multipart/mixed — Email with attachments

MIME Types in HTTP

The Content-Type header tells the recipient what format the response body is in:

HTTP/1.1 200 OK
Content-Type: application/json; charset=UTF-8

{"status": "ok"}

The Accept header tells the server what formats the client can handle:

GET /api/users HTTP/1.1
Accept: application/json, text/plain, */*

Content-Type in HTML Forms

HTML form encoding is controlled by the enctype attribute:

<!-- URL-encoded (default) -->
<form method="post" enctype="application/x-www-form-urlencoded">

<!-- Required for file uploads -->
<form method="post" enctype="multipart/form-data">

Common MIME Type Pitfalls

application/octet-stream

The generic binary type. Browsers download rather than display files with this type. Use specific types for correct browser handling.

text/javascript vs. application/javascript

Both are widely used; modern spec recommends text/javascript. In practice, both work in browsers.

application/x-www-form-urlencoded vs. multipart/form-data

For API POST requests with JSON body, use application/json. Use multipart/form-data only when uploading actual binary files.

MIME Sniffing

Some browsers ignore the declared Content-Type and "sniff" the actual content to determine the type. This can be a security risk. The X-Content-Type-Options: nosniff header prevents this behavior.

File Extensions to MIME Types

Common mappings:

Using the MIME Types Reference Tool

Our tool:

1. Search by extension — find the MIME type for any file extension
2. Search by MIME type — find the file extension for any MIME type
3. Browse categories — explore all types in a category
4. Copy type — one-click copy for use in code
5. See browser support — which types browsers handle natively

Essential reference for web developers setting Content-Type headers, handling file uploads, and configuring web servers.