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TLDR reference

MIME types

A searchable reference mapping file extensions to their MIME type, the Content-Type that tells software how to handle a file. Type to search, or filter by kind. Everything runs in your browser.

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How it works

A searchable reference mapping file extensions to their MIME type, the label that tells software how to handle a file. A MIME type (also called a media type or content type) looks like type/subtype - text/html, image/png, application/json - and it is what a server puts in the Content-Type header so the browser knows whether to render, play, or download what it just received. Type to search by extension or by type, or use the chips to browse a single kind such as images or fonts.

It covers the everyday web formats alongside the office documents and archives whose types are long and easy to forget, like the Office Open XML type for a .docx file. Each entry gives the canonical type and a short note. Everything is static and runs in your browser, so the lookup is instant and works offline once the page has loaded.

Example. Searching "json" shows application/json, the type to send for an API response, while filtering by the Font chip lines up font/woff2, font/woff, font/ttf, and font/otf so you can set the right type when serving web fonts.

FAQ

What is a MIME type?

A MIME type is a standard label that identifies the format of a file or piece of data, written as type/subtype, such as text/css or image/jpeg. It originated in email (MIME stands for Multipurpose Internet Mail Extensions) but is now used everywhere on the web. When a server sends a response, it states the MIME type in the Content-Type header, and the browser uses that - not the file extension - to decide how to treat the bytes it receives.

Why does the Content-Type matter more than the file extension?

On the web, the browser trusts the Content-Type header, not the URL or extension. If a server sends a stylesheet with the wrong type, the browser may refuse to apply it; if it sends a script as text/plain, the script will not run. This is also a security boundary: the X-Content-Type-Options: nosniff header tells the browser not to second-guess the declared type. Setting the correct MIME type on your server is what makes files behave as intended.

What is application/octet-stream?

It is the generic "arbitrary binary data" type, the catch-all when the real format is unknown. Because the browser cannot render unknown binary data, serving a file as application/octet-stream typically triggers a download rather than an inline display, which is sometimes used deliberately to force a "save as". When you can identify the real type, though, it is better to send it so the file opens correctly.

Why are the Office document types so long?

The modern Office formats (.docx, .xlsx, .pptx) are based on the Office Open XML standard, and their MIME types spell that lineage out in full, such as application/vnd.openxmlformats-officedocument.wordprocessingml.document for a Word file. The vnd. prefix marks them as vendor-specific types registered with IANA. They are tedious to type but unambiguous, which is the point; this reference lists them so you can copy the exact string rather than memorise it.