MIM
Extension to MIME
Look up the MIME type for a file extension.
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How to use Extension to MIME
Look up the MIME type for a file extension.
- Type a file extension such as json or png, with or without the leading dot.
- Press Run to see the standard internet media type for it.
- Copy the MIME string into your server config or response headers.
Practical note. The tool looks up the registered MIME type for common file extensions; uncommon or vendor-specific extensions may fall back to a generic type such as application/octet-stream.
When you actually reach for this
- You are serving a file and need the correct Content-Type header from its extension.
- You want to validate that an uploaded file's extension matches a sane MIME type before processing it.
Where this tool stops being accurate
- Extension-to-MIME is a lookup, not content inspection — a .png renamed to .jpg still reports image/jpeg though the bytes lie.
- Some extensions map to several MIME types (e.g. .js can be application/javascript or text/javascript) depending on convention.
Frequently asked questions
What does Extension to MIME do?
Look up the MIME type for a file extension.
The MIME type is wrong for my framework — can I override it?
Yes, the mapping is a suggestion; set the header your stack expects. Just keep it consistent so browsers interpret the file correctly.
Should I trust the extension for security?
No — inspect actual bytes (magic numbers) if you must enforce a type; the extension is user-controlled and easily faked.