Mime Lookup
Mime Lookup — runs in your browser. Inputs are not stored.
Extension → MIME lookup
Enter values, then press Calculate.
How to use
- In extension or file name, enter something like png, photo.jpg, or .webp.
- Press Look up to see the normalized extension and MIME type. Letter case is folded to lowercase.
- Use Copy to grab the MIME string for a Content-Type header or your code.
- Extensions not in the table show as unknown. This is not the full IANA list.
- Reset clears the field. There is no reverse lookup from MIME type to extension.
Key concepts
MIME type lookup is a local table for quickly mapping an extension to a Content-Type when you write upload allowlists, nginx types, or an HTML accept attribute. It covers common entries such as jpg → image/jpeg and json → application/json. It does not replace the Content-Type your server actually sends. If jpg and jpeg both map to image/jpeg, that is expected; if the server sends something else, trust the server config. Unfamiliar extensions showing as unknown is normal—the table is a short reference, not a complete registry.
The result is not always the same as the Content-Type a server sends. Lookup uses a static mapping in the browser only. Vendor-specific types and the full IANA list may be missing, so if you see unknown, check the official registry. There is no MIME→extension reverse lookup.
Example
Looking up photo.jpg yields extension jpg and MIME image/jpeg. .WEBP with a leading dot and capitals still normalizes to webp. xyz is unknown. The copy button can copy image/jpeg. file.PNG and .png both become image/png. json is commonly application/json; webp is image/webp; pdf is application/pdf. File.JPEG normalizes to jpeg.
Related: URL parser
Frequently asked questions
Is this MIME lookup the full official IANA list?
No. It only includes common entries. Not every extension is listed. Missing ones show as unknown.
What happens if the extension is not in the table?
It is shown as unknown. Letter case is folded to lowercase before the table is checked.
Does letter case affect MIME lookup?
Values are normalized to lowercase. The result can still differ from the headers a server actually sends.
Does this MIME type guarantee the server Content-Type?
It is for reference only. Check the real server configuration. There is no reverse lookup from MIME type to extension.
Can I look up an extension from a MIME type?
Currently only extension→MIME is supported. For archive.tar.gz, the last segment (gz) is used. If there are several dots, the last extension is used.
If the file name has several dots, which extension is used?
The last extension. Example: archive.tar.gz uses gz. The lookup string is not stored.
Last reviewed: 2026-09-04