MIME Type Lookup -- Content-Type by Extension

Search MIME Types

What Is a MIME Type?

A MIME type (Multipurpose Internet Mail Extensions type) is a standardized label that identifies the format of a file or data stream on the internet. When a web server sends a file to a browser, it includes the MIME type in the Content-Type HTTP header so the browser knows how to handle the response — whether to render HTML, display an image, play audio, or prompt a download.

MIME types were originally developed for email attachments (RFC 2045, 1996) but are now used across HTTP, APIs, file systems, and virtually every internet protocol that transfers data.

MIME Type Structure

Every MIME type follows the type/subtype format:

type/subtype

• type — The broad category: image, video, audio, text, application, font, or multipart
• subtype — The specific format: jpeg, png, mp4, plain, json, pdf

An optional parameter can follow, separated by a semicolon. The most common parameter is charset:

Content-Type: text/html; charset=utf-8
Content-Type: application/json
Content-Type: image/png
Content-Type: multipart/form-data; boundary=----WebKitFormBoundary

The Seven Top-Level Types

MIME Type vs File Extension

File extensions (.jpg, .pdf) and MIME types (image/jpeg, application/pdf) both identify file formats, but they work differently:

Key point: Browsers use the MIME type from the Content-Type header, not the file extension in the URL. A file named data.txt served with Content-Type: application/json is treated as JSON.

How to Set MIME Types on Your Server

Correct MIME type configuration prevents rendering issues and security warnings.

Apache (.htaccess)

AddType application/json .json
AddType font/woff2 .woff2
AddType image/webp .webp
AddType image/avif .avif

Nginx (mime.types or server block)

types {
    application/json  json;
    font/woff2        woff2;
    image/webp        webp;
    image/avif        avif;
}

Node.js / Express

res.setHeader('Content-Type', 'application/json; charset=utf-8');
res.sendFile('data.json');

Most frameworks handle common types automatically. Manual configuration is mainly needed for newer formats like AVIF, WOFF2, or WebAssembly.

Common Mistakes

• Serving JavaScript as text/plain: Modern browsers enforce MIME type checking for scripts. If a .js file is served with the wrong Content-Type, the browser blocks execution with a MIME type mismatch error.
• Missing charset=utf-8 for text types: Without an explicit charset, browsers may guess the encoding incorrectly, causing garbled characters. Always include charset=utf-8 for text/html, text/css, text/javascript, and application/json.
• Using application/x-javascript instead of text/javascript: The x- prefix was for experimental types. text/javascript is the official registered type for JavaScript (RFC 9239).
• Serving SVG as text/xml or image/xml: The correct MIME type is image/svg+xml. Using the wrong type prevents browsers from rendering the SVG inline.
• Confusing application/x-www-form-urlencoded with multipart/form-data: Use application/x-www-form-urlencoded for simple form fields. Use multipart/form-data when the form includes file uploads.
• Assuming file extension determines behavior: A file named image.png served as text/html is treated as HTML by the browser, not as an image. The MIME type in the header always takes precedence.

Frequently Asked Questions

What is a MIME type?

A MIME type is a standardized label that identifies the format of a file or data stream. It follows the type/subtype pattern — for example, image/png or application/json. Web servers include MIME types in the Content-Type HTTP header so browsers know how to handle the response.

What is the difference between MIME type and Content-Type?

They refer to the same thing in practice. MIME type is the format label itself (e.g., text/html). Content-Type is the HTTP header that carries the MIME type, sometimes with additional parameters like charset. Example: Content-Type: text/html; charset=utf-8.

What is the MIME type for JSON?

The MIME type for JSON is application/json. Use this in API responses, AJAX requests, and anywhere you send or receive structured JSON data.

What is the MIME type for PDF?

The MIME type for PDF is application/pdf. Servers use this Content-Type so browsers display or download the PDF correctly.

What happens if the wrong MIME type is set?

Browsers may refuse to execute scripts (MIME type mismatch), display a download dialog instead of rendering content, or fail to apply stylesheets. For example, serving CSS as text/plain causes browsers to ignore the stylesheet entirely.

Are MIME types case-sensitive?

No. MIME types are case-insensitive per the HTTP specification. image/PNG and image/png are equivalent. However, the convention is lowercase, and all major registries use lowercase.

What MIME type should I use for file uploads?

For generic binary uploads where the type is unknown, use application/octet-stream. For HTML form uploads with files, the browser automatically sets multipart/form-data. For specific formats, match the MIME type to the file — image/jpeg for JPEG, application/pdf for PDF, etc.

What is the difference between text/plain and application/octet-stream?

text/plain tells the browser the content is human-readable text that can be displayed directly. application/octet-stream indicates arbitrary binary data — browsers typically prompt a file download. Use text/plain for readable text; use application/octet-stream for unknown or binary files.

Where are MIME types officially registered?

IANA (Internet Assigned Numbers Authority) maintains the official registry at iana.org/assignments/media-types. The registry defines standard types and their specifications.

What is the MIME type for SVG?

The MIME type for SVG is image/svg+xml. The +xml suffix indicates that SVG is an XML-based format.

How do I set MIME types on my web server?

On Apache, use AddType directives in .htaccess. On Nginx, edit the mime.types file or add types blocks. On Node.js/Express, set the Content-Type header or use the mime-types package. Most frameworks handle common types automatically.

What is a multipart MIME type?

Multipart MIME types contain multiple parts, each with its own Content-Type. The most common is multipart/form-data, used for HTML form submissions with file uploads. Each part is separated by a boundary string defined in the Content-Type header.

Related Tools

• URL Encoder/Decoder — encode and decode URLs and query parameters
• Base64 Encoder/Decoder — encode binary data as text for embedding or transport
• JSON Formatter — format and validate JSON data
• Meta Tag Generator — generate HTML meta tags including Content-Type
• Data Size Converter — convert between bytes, KB, MB, GB, and TB
• MIME Types Explained: What They Are and How They Work — in-depth guide to MIME types, Content-Type headers, and server configuration

Privacy & Limitations

• Client-side only. No data is sent to any server. The MIME type database is embedded in this page and all lookups happen in your browser.
• Database scope. This tool includes 80+ of the most common MIME types. Some rare or vendor-specific types may not be listed. The IANA registry contains thousands of entries.
• No file inspection. This tool looks up MIME types by file extension, not by inspecting actual file contents. A file's true format may differ from its extension.
• Convention, not detection. Extensions like .ogg map to both video/ogg and audio/ogg depending on content. This tool shows both mappings.

MIME Type Lookup FAQ