MIME types

THE PRACTICAL GUIDE · NORMANDIN SYSTEMS

Get more from MIME types

MIME Types helps map common file extensions to media types and look up extensions associated with a known type. A media type describes how content should be interpreted, often through an HTTP Content-Type header. A filename extension is a naming convention and can be misleading, so a lookup provides a likely mapping rather than proof of a file's actual encoded contents. A cheatsheet works best as a memory aid while you practice a concrete task. Read the command or syntax together with its arguments, placeholders, and surrounding context. Similar-looking options can have very different meanings, and an example written for one platform or version may need adjustment elsewhere. Keep the reference beside a small test case, use read-only examples first when possible, and check the relevant help output before applying an unfamiliar command to valuable files or a running service.

Guide updated October 13, 2026

How to use this tool

1. Identify the operation you want to perform and find the matching section of the reference. Read the whole example before copying any part of it.
2. Enter an extension or MIME type and inspect the corresponding values returned by the lookup.
3. Review the example below and compare its expected behavior with a small sample of your own input before continuing.
4. Try the adapted example on a small test case, compare the result with the explanation, and save the command with a note about the context in which it works.

SEE IT IN PRACTICE

A worked example

Extension .png

Media type image/png

The mapping is commonly used when serving a PNG image, while the actual file still needs to contain valid PNG data.

A media type is not a file conversion

Changing a server header or filename extension does not rewrite the underlying data. A JPEG served as image/png is still JPEG-encoded content, even if some software detects and tolerates the mismatch. Use the lookup to identify a conventional mapping, then verify the actual file format. Upload validators and servers may apply additional rules, and an extension can map ambiguously in some ecosystems. The receiving application's accepted formats remain the practical requirement.

Content-Type and content handling

For web responses, Content-Type helps a client interpret the resource, while other headers can influence download behavior, caching, and security. A correct MIME type is one part of a correct response, not the entire configuration. Test the resource's response headers and how it opens in the intended client. For text formats, character encoding is another important detail. A lookup can suggest text/plain or application/json, but it cannot determine whether the actual bytes use the encoding your application expects.

When this tool is useful

• Set an appropriate response Content-Type
• Interpret a file-upload format requirement
• Look up a common extension for a media type

Tips for a better result

• Compare the mapping with the actual file format and the requirements of the application or server that will consume it.
• Replace example paths, identifiers, and names deliberately. Copying a reference command unchanged can target a different file, branch, service, or environment from the one you intended.
• Keep the source and the settings used for this result together. That makes a later comparison or correction easier, especially when another person needs to reproduce the same outcome.

Frequently asked questions