3 MIME Type Lookup Tools, Compared

A file downloads as download with no extension, or a browser renders your PDF as a wall of text. Both are the same problem: the Content-Type header is wrong, and you need the right string for a .woff2, a .heic or whatever else has landed in the upload folder.

The values are not guessable. application/javascript and text/javascript have swapped places in guidance over the years, fonts have their own family of types, and half the formats in daily use were never formally registered at all. So you look it up — and where the tool gets its list from turns out to matter.

How to judge a MIME type lookup

Where does the data come from? The IANA registry is authoritative but incomplete in practice. Server defaults from Nginx and Apache reflect what actually works. The best tools combine them.

Does it go both ways? Extension to type is the common direction. Type to extension matters when you are handed a Content-Type and need to name the file.

Does it cover modern formats? AVIF, HEIC, WebP and Opus are the usual test. A stale table will not have them.

Does it work offline? A reference you can use on a plane or inside a locked-down network is worth more than one that needs a round trip.

The comparison

Facts checked August 2026; tools change. Table covers only the 3 alternatives — our tool gets its own section below.

ZeroUtil MIME Type Lookup

The most rigorous about provenance, which is the thing that separates a good MIME reference from a copied table. Its list combines the IANA Media Types registry, the mime.types file shipped with Nginx, the Apache httpd mime.types file, and a handful of community-tracked formats including AVIF, HEIC, WebP and Opus — so it covers both what is registered and what servers actually send.

You can search by extension or descriptive keyword, filter by category (application, audio, image, text, video, font), copy with one click and see every extension mapped to a given type. The full list is bundled into the page at build time and searched client-side, so it works offline after the first load with no API call, no external lookup and no telemetry on your queries. Free, no account.

Gera Tools MIME Lookup

The quickest of the three, with a neat trick: one input box that works out what you meant. Type something containing a slash, like application/pdf, and it treats it as a MIME type and returns the extensions; type anything else and it treats it as an extension and returns the type. No mode switch to think about.

It runs entirely offline in the browser with nothing uploaded and no network request, free and with no account. The interface is minimal to the point of being terse — you get the answer and not much context, which is either exactly right or slightly thin depending on whether you already know what you are looking at.

Aback Tools MIME Type Lookup

Part of a large browser-based utility platform — over 1,300 tools across a dozen categories — so it is the one to bookmark if you would rather have one site for conversions, PDF work and reference lookups together. Coverage spans image formats including RAW camera types, data formats like JSON, YAML and Protocol Buffers, documents, media and archives, most of them IANA-registered.

It states no signup, no rate limits, no premium tiers, and that processing happens in the browser via JavaScript and WebAssembly so files never leave your device. What it does not state is how many MIME types the lookup actually covers, so an unusual extension is worth verifying elsewhere.

MIME Type Lookup

Ours is a searchable reference table of common file extensions and their MIME types, filtering live as you type, entirely in the browser. The design goal is speed for the common case: you know the extension, you want the string, you do not want to think about categories or modes first.

What it does not do: document its sources the way ZeroUtil does, or reverse a Content-Type back into extensions from the same box the way Gera Tools does. For an unusual or disputed type, the IANA Media Types registry is the authority worth checking against — every tool here is downstream of it.

Which one to pick

• You need to justify a value to someone — ZeroUtil, which shows where it came from.
• You have a Content-Type and need the extension — Gera Tools’ single box.
• You want one site for everything — Aback Tools.
• You know the extension and want the string now — the tool below.

How to do it with MIME Type Lookup

1. Open the MIME Type Lookup and start typing the extension.
2. Read the matching Content-Type value from the filtered table.
3. Set it on your server or in your upload handler — do not rely on the browser guessing.
4. Verify by checking the response header on a real request.

The walkthrough is in how to look up a MIME type by file extension. Other developer tools are in the tools directory.

You might also need

Once the value is set, the HTTP Headers Parser shows what the server is actually sending — which is frequently not what you configured.

Frequently asked questions

Is there a free MIME type lookup that doesn’t need an account?

All four here are free with no account, and ZeroUtil, Gera Tools and ours all run client-side, so your queries are not sent anywhere. ZeroUtil and Gera Tools also keep working offline after the first load.

What is the correct MIME type for JavaScript?

text/javascript is the type IANA now records for JavaScript, after years of application/javascript being the common recommendation. Both are widely accepted by browsers, which is why the confusion persisted so long.

Why does my file download instead of displaying?

Usually a Content-Type of application/octet-stream, which tells the browser “unknown binary, save it”. Setting the correct specific type generally fixes it — though a Content-Disposition: attachment header will force a download regardless.

Final thought

Set the type explicitly on the server rather than hoping something infers it. Browsers guess, guess differently from each other, and the guess that works in Chrome today is not a specification.

Try the free MIME Type Lookup