What is mime?
The mime npm package is a utility for handling and transforming file MIME types. It provides functionality to lookup the MIME type for a file based on its extension, determine the default extension for a MIME type, and define custom MIME type mappings.
What are mime's main functionalities?
Lookup MIME type by extension
This feature allows you to get the MIME type for a given file extension. In the code sample, we are looking up the MIME type for a '.json' file, which returns 'application/json'.
const mime = require('mime');
const mimeType = mime.getType('json'); // 'application/json'
Lookup extension by MIME type
This feature enables you to find the default file extension for a given MIME type. In the code sample, we are finding the extension for the MIME type 'application/json', which returns 'json'.
const mime = require('mime');
const extension = mime.getExtension('application/json'); // 'json'
Define custom MIME type mappings
This feature allows you to define custom MIME type mappings. In the code sample, we are adding a custom MIME type 'text/x-some-format' with multiple extensions. The second argument 'true' indicates that the custom types should take precedence over the built-in types.
const mime = require('mime');
mime.define({ 'text/x-some-format': ['x-sf', 'x-sft', 'x-sfml'] }, true);
Other packages similar to mime
mime-types
The 'mime-types' package is similar to 'mime' in that it provides MIME type lookup based on file extension and vice versa. It is based on the mime-db dataset, which is a comprehensive dataset of MIME types compiled from various sources. Compared to 'mime', it might offer a more extensive and updated list of MIME types.
file-type
The 'file-type' package goes beyond simple MIME type lookup by extension; it can detect the actual MIME type of a file or a Buffer by checking the file's magic numbers (file signatures). This can be more reliable than 'mime' when dealing with files that have incorrect or missing extensions.
Mime
A comprehensive, compact MIME type module.
Install
NPM
npm install mime
Browser
It is recommended that you use a bundler such as
webpack or browserify to
package your code. However, browser-ready versions are available via
skypack.dev as follows:
// Full version
<script type="module">
import mime from "https://cdn.skypack.dev/mime";
</script>
// "lite" version
<script type="module">
import mime from "https://cdn.skypack.dev/mime/lite";
</script>
Quick Start
For the full version (800+ MIME types, 1,000+ extensions):
const mime = require('mime');
mime.getType('txt');
mime.getExtension('text/plain');
See Mime API below for API details.
Lite Version
The "lite" version of this module omits vendor-specific (*/vnd.*
) and
experimental (*/x-*
) types. It weighs in at ~2.5KB, compared to 8KB for the
full version. To load the lite version:
const mime = require('mime/lite');
Mime .vs. mime-types .vs. mime-db modules
For those of you wondering about the difference between these [popular] NPM modules,
here's a brief rundown ...
mime-db
is "the source of
truth" for MIME type information. It is not an API. Rather, it is a canonical
dataset of mime type definitions pulled from IANA, Apache, NGINX, and custom mappings
submitted by the Node.js community.
mime-types
is a thin
wrapper around mime-db that provides an API drop-in compatible(ish) with mime @ < v1.3.6
API.
mime
is, as of v2, a self-contained module bundled with a pre-optimized version
of the mime-db
dataset. It provides a simplified API with the following characteristics:
- Intelligently resolved type conflicts (See mime-score for details)
- Method naming consistent with industry best-practices
- Compact footprint. E.g. The minified+compressed sizes of the various modules:
Module | Size |
---|
mime-db | 18 KB |
mime-types | same as mime-db |
mime | 8 KB |
mime/lite | 2 KB |
Mime API
Both require('mime')
and require('mime/lite')
return instances of the MIME
class, documented below.
Note: Inputs to this API are case-insensitive. Outputs (returned values) will
be lowercase.
new Mime(typeMap, ... more maps)
Most users of this module will not need to create Mime instances directly.
However if you would like to create custom mappings, you may do so as follows
...
const Mime = require('mime/Mime');
const typeMap = {
'text/abc': ['abc', 'alpha', 'bet'],
'text/def': ['leppard']
};
const myMime = new Mime(typeMap);
myMime.getType('abc');
myMime.getExtension('text/def');
If more than one map argument is provided, each map is define()
ed (see below), in order.
mime.getType(pathOrExtension)
Get mime type for the given path or extension. E.g.
mime.getType('js');
mime.getType('json');
mime.getType('txt');
mime.getType('dir/text.txt');
mime.getType('dir\\text.txt');
mime.getType('.text.txt');
mime.getType('.txt');
null
is returned in cases where an extension is not detected or recognized
mime.getType('foo/txt');
mime.getType('bogus_type');
mime.getExtension(type)
Get extension for the given mime type. Charset options (often included in
Content-Type headers) are ignored.
mime.getExtension('text/plain');
mime.getExtension('application/json');
mime.getExtension('text/html; charset=utf8');
mime.define(typeMap[, force = false])
Define [more] type mappings.
typeMap
is a map of type -> extensions, as documented in new Mime
, above.
By default this method will throw an error if you try to map a type to an
extension that is already assigned to another type. Passing true
for the
force
argument will suppress this behavior (overriding any previous mapping).
mime.define({'text/x-abc': ['abc', 'abcd']});
mime.getType('abcd');
mime.getExtension('text/x-abc')
Command Line
mime [path_or_extension]
E.g.
> mime scripts/jquery.js
application/javascript
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