How does the browser know the MIME if the server omits the header?

The browser **guesses** - looks at the extension and the first few bytes of the file (magic numbers). This is unreliable. In strict security mode (`X-Content-Type-Options: nosniff`) some browsers outright **block** responses with no Content-Type.

Why "image/jpeg" and not "image/jpg"?

Because the IANA-registered MIME uses the full word "jpeg", not the abbreviation "jpg". The file extension (`.jpg` or `.jpeg`) is a separate thing - both are valid for this MIME. Rule: always write **image/jpeg** in HTTP headers, never image/jpg.

What is the difference between text/javascript and application/javascript?

Historically people used `application/javascript`, but as of 2022 **the HTML spec officially recommends text/javascript**. Most servers send text/javascript today. Application/javascript is **deprecated** - it still works, but for new projects prefer text.

What is multipart/form-data and when do I use it?

It is the MIME for HTML forms that upload **files** (` `). Instead of plain `application/x-www-form-urlencoded`, the body is split into parts each with its own headers. Required for anything binary. The frontend sends it automatically when the form has `enctype="multipart/form-data"`.

Why does application/octet-stream exist?

It is the **universal fallback** for unknown binary types. Most browsers, seeing it, **force a download** instead of trying to render. Use it when the response is raw bytes, when you return an unknown format, or together with `Content-Disposition: attachment` to force a save dialog.

Why image/x-icon instead of image/icon?

The **x-** prefix historically meant "experimental" - it was used for types outside the official registry. Today new types do not use the prefix, but for backward compatibility no one renames the old ones. For favicons, both `image/x-icon` and `image/vnd.microsoft.icon` are valid.

How do I open a MIME types lookup in the browser?

The page you are reading right now **is** the lookup. You can also try `chrome://about-mime-types` in Chrome (internal page) or run `file --mime-type filename.xyz` in a Linux/macOS terminal to detect the type from content.

Does the MIME include the character encoding?

No. Encoding goes in the **charset parameter**: `Content-Type: text/html; charset=utf-8`. UTF-8 is the default for most text types. Always state it explicitly for `text/*` to avoid surprises.

What are vendor-specific types (vnd.*) and x-* prefixes?

`application/vnd.*` are types registered by a **specific vendor** (e.g. `application/vnd.openxmlformats-officedocument.wordprocessingml.document` is Microsoft Word). `x-*` are old unregistered types (e.g. `application/x-yaml`). For new projects, try to use an officially IANA-registered MIME.

MIME Type Lookup - free

Showing 108 of 108 types

Results

MIME type

image/png

PNG image

imagebrowser nativepopular

Extensions

When to use it

Lossless raster, transparency, screenshots.

HTTP header

Content-Type: image/png

↑↓navigate the listEntercopy first hit

What is a MIME type and how do I find one?

A MIME type tells browsers and servers what is inside a file: "image/png", "application/pdf", "text/html". Without the right MIME, browsers will either force a download or show garbage.

This is a two-way search across 300+ types. Type an extension (.pdf → application/pdf), a MIME (application/json → .json), or a name ("PNG image" → image/png, .png).

It all runs offline because the data is baked into the page. The most popular types are starred, deprecated ones (like image/jp2) come with a warning and a suggested replacement.

How to use it

Type an extension (.pdf, png, mp4), a MIME (image/png, application/json), or a description (Excel, PDF, audio MP3).

The list filters instantly. Click a category - Image / Audio / Video / Application / Text / Font / 3D Model - to narrow it down.

Arrow keys ↑↓ move the highlight, Enter copies the MIME of the first hit.

Click any entry to see the detail panel: extensions, category, when to use it, ready Content-Type header, whether browsers render it natively.

Copy buttons grab just the MIME, just the extension, or the full HTTP header to paste straight into code.

When this is useful

Everyday MIME situations for developers:

Sending a file via API - what Content-Type for XLSX? `application/vnd.openxmlformats-officedocument.spreadsheetml.sheet`. Check it here in 2 seconds.
Accepting uploads - your client sends a file, you validate `req.headers['content-type']`. Which values should "image" accept? `image/png`, `image/jpeg`, `image/webp`, `image/avif`, `image/gif`. All starred as "popular".
Nginx / Apache config - you add `AddType` for a new extension. `.woff2 → font/woff2`. `.webmanifest → application/manifest+json`.
Service worker in a PWA - you must respond with the correct MIME or the browser rejects the resource. Look it up here.
HTML5 video/audio - which containers play natively in the browser? Filter by "browser native" - they are flagged.
Old formats - a customer says "I uploaded a WMV". You see it is `video/x-ms-wmv` and deprecated - suggest a conversion to MP4.
Magic numbers - you know only the extension and need the MIME. Type `.jp2` and discover JPEG 2000 is deprecated.

Related tools: the HTTP request tester tells you what your server actually returns. The HTTP headers inspector pulls every header out of a response.

Questions and answers

A MIME type (Multipurpose Internet Mail Extensions) is a `type/subtype` string describing the file content. Born in 1990s email, used everywhere today - in HTTP (`Content-Type: image/png`), forms, drag-and-drop, clipboards, file saves.

What is a MIME type and how do I find one?

A MIME type tells browsers and servers what is inside a file: "image/png", "application/pdf", "text/html". Without the right MIME, browsers will either force a download or show garbage.

This is a two-way search across 300+ types. Type an extension (.pdf → application/pdf), a MIME (application/json → .json), or a name ("PNG image" → image/png, .png).

It all runs offline because the data is baked into the page. The most popular types are starred, deprecated ones (like image/jp2) come with a warning and a suggested replacement.

How to use it

Type an extension (.pdf, png, mp4), a MIME (image/png, application/json), or a description (Excel, PDF, audio MP3).

The list filters instantly. Click a category - Image / Audio / Video / Application / Text / Font / 3D Model - to narrow it down.

Arrow keys ↑↓ move the highlight, Enter copies the MIME of the first hit.

Click any entry to see the detail panel: extensions, category, when to use it, ready Content-Type header, whether browsers render it natively.

Copy buttons grab just the MIME, just the extension, or the full HTTP header to paste straight into code.

When this is useful

Everyday MIME situations for developers:

Sending a file via API - what Content-Type for XLSX? `application/vnd.openxmlformats-officedocument.spreadsheetml.sheet`. Check it here in 2 seconds.
Accepting uploads - your client sends a file, you validate `req.headers['content-type']`. Which values should "image" accept? `image/png`, `image/jpeg`, `image/webp`, `image/avif`, `image/gif`. All starred as "popular".
Nginx / Apache config - you add `AddType` for a new extension. `.woff2 → font/woff2`. `.webmanifest → application/manifest+json`.
Service worker in a PWA - you must respond with the correct MIME or the browser rejects the resource. Look it up here.
HTML5 video/audio - which containers play natively in the browser? Filter by "browser native" - they are flagged.
Old formats - a customer says "I uploaded a WMV". You see it is `video/x-ms-wmv` and deprecated - suggest a conversion to MP4.
Magic numbers - you know only the extension and need the MIME. Type `.jp2` and discover JPEG 2000 is deprecated.

Related tools: the HTTP request tester tells you what your server actually returns. The HTTP headers inspector pulls every header out of a response.

Questions and answers

MIME Type Lookup

What is a MIME type and how do I find one?

How to use it

When this is useful

Questions and answers

Related tools

HTTP Status Codes

HTTP Headers Reference

HTTP Headers Inspector

File Converter

MIME Type Lookup

What is a MIME type and how do I find one?

How to use it

When this is useful

Questions and answers

Related tools

HTTP Status Codes

HTTP Headers Reference

HTTP Headers Inspector

File Converter