DataHub Tools MIME Type Lookup

MIME Type Lookup

Local-first

Look up common file extensions and MIME types for web headers and uploads.

How this tool actually works

This lookup checks a small built-in mapping of common extensions and media types. It searches in either direction, removes parameters such as charset for lookup, and returns all mapped extensions, but it is not the IANA registry and does not inspect file contents.

  • Look up common extensions
  • Reverse-look up common media types
  • Keep reference checks local

How to use it

  1. Enter an extension such as .json or a bare media type such as application/json.
  2. Compare the result with the IANA registry or the receiving system's documentation.
  3. Remove parameters such as charset before using this limited reverse lookup.
  4. Never use the result alone to establish an uploaded file's real content.

Quick example

Example input

.json
application/json
text/html; charset=UTF-8

Expected result

.json -> application/json
application/json -> .json
text/html; charset=UTF-8 -> .html, .htm

A filename extension is a convention, not content detection. Attackers can rename files, and HTTP Content-Type can include parameters.

Best use cases

  • Recall a common Content-Type value.
  • Check a familiar extension during configuration.
  • Identify when an authoritative registry lookup is needed.

References and scope

IANA maintains the registered media-type list, RFC 6838 defines registration structure, and HTTP defines Content-Type semantics. This page is only a small convenience map.

Sources checked July 24, 2026. Specifications and platform behavior can change; verify the sources before formal use.

Known limitations

  • Vendor, experimental, uncommon, and multi-suffix types are mostly absent.
  • Reverse lookup returns every extension present in this small map.
  • Security validation must inspect content and enforce an application allowlist.

FAQ

Does it use the full IANA registry?

No. It uses a small hard-coded list of common mappings.

Can it detect an uploaded file?

No. It does not read file bytes or perform content sniffing.

Can one type return multiple extensions?

Yes, when multiple entries in the built-in map share that media type.

Are charset parameters supported?

Parameters are removed before lookup, so text/html; charset=UTF-8 is treated as text/html.

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