Developer Tools

Look Up a MIME Type

100% Free No Signup Runs in Browser

Mime Type Lookup for quick browser-based work with focused input and copy-ready output.

Direct Answer

Use the MIME Type Lookup when you need the correct Content-Type value for a file extension, such as when configuring an upload form, API response header, or server MIME mapping.

How a MIME Type Is Structured

Every MIME type is a two-part string in the form type/subtype, and both halves carry meaning about how the data should be interpreted or handled.

  • The type (like text, image, application, audio, video) is the broad category.
  • The subtype (like plain, png, json, mp4) narrows it down to the specific format.
  • A vendor or structured suffix, like application/vnd.api+json, signals a specific vendor format built on a general syntax.
  • MIME type names are conventionally lowercase, though the comparison itself is case-insensitive.

Where MIME Type Mismatches Cause Problems

A wrong or missing MIME type is a frequent, hard-to-diagnose cause of uploads being rejected or API requests failing for reasons that have nothing to do with the actual data.

  • A file's extension can lie about its real content; a renamed .txt to .json doesn't change what's actually inside it.
  • An API expecting application/json will often reject a request sent with a Content-Type of text/plain, even if the body is valid JSON.
  • Browsers and servers sometimes perform MIME sniffing, inspecting the actual bytes rather than trusting the declared type, which can produce different behavior than expected.
  • Strict upload whitelists that check MIME type rather than file extension will reject files whose declared type doesn't match what's allowed.

How to Use Mime Type Lookup

  1. Open the tool on this page.
  2. Enter or paste your input in the field provided.
  3. Review the result shown on the page, then copy or download it.

Reference

FeatureDetails
PurposeComplete the utility task shown on this page.
InputThe value or content requested by the tool.
ResultThe generated or processed output shown on the page.
Best forQuick browser-based utility work.
CategoryDeveloper Tools
Works onDesktop, tablet, and mobile browsers

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Frequently Asked Questions

What is a MIME type?

A MIME type is a standardized two-part label, written as type/subtype, that tells a browser, server, or application how to interpret a piece of data. It's used in HTTP Content-Type headers, email attachments, and file handling to communicate what kind of content follows.

What's the MIME type for common files like .json, .pdf, .png, and .csv?

A .json file is application/json, a .pdf is application/pdf, a .png image is image/png, and a .csv file is text/csv. These are the standard registered types most servers and browsers recognize by default.

Is application/octet-stream the same as 'unknown file type'?

It's the generic fallback MIME type for arbitrary binary data when a more specific type can't be determined. It effectively tells the receiving application "treat this as raw bytes," which is why browsers usually download rather than try to render a file served with this type.

Can a file's extension lie about its real content?

Yes, renaming a file changes only its extension, not the actual bytes inside it, so a malicious or mislabeled file can have an extension that doesn't match its true format. This is exactly why security-conscious upload handling checks the file's actual content signature (magic number) rather than trusting the extension alone.

Why did my API reject a request with the wrong Content-Type?

Many APIs strictly check the Content-Type header and refuse to parse the body if it doesn't match what they expect, even when the body itself is perfectly valid. Sending JSON with a Content-Type of text/plain instead of application/json is a common cause of an API returning an unhelpful 400 or 415 error.

Are MIME types case-sensitive?

The MIME type specification itself is case-insensitive for comparison purposes, but the convention is to write them in lowercase, like application/json rather than Application/JSON. Most software normalizes to lowercase internally regardless of how the value was received.

What's the difference between text/plain and application/json for the same content?

The bytes can be identical, but the declared MIME type changes how the receiving system treats them; text/plain tells a client to display raw text, while application/json signals the content should be parsed as JSON. A file renamed from .txt to .json doesn't automatically fix its Content-Type if the server is still declaring it as plain text.

Why does a browser sometimes ignore the declared MIME type?

Browsers perform MIME sniffing in certain situations, inspecting the actual byte content to guess the real type rather than trusting a possibly incorrect or missing Content-Type header. This behavior can be disabled with the X-Content-Type-Options: nosniff header when a server wants its declared type respected exactly.

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