mrmime

library0.0.1jsnpmunverified

mrmime is a minimalist and high-performance utility designed to retrieve MIME types from file extensions or filenames. Currently at version 2.0.1, it offers a small footprint (2.8kB gzipped) and O(1) lookup times, making it significantly faster than alternatives like `mime` or `mime/lite` as demonstrated in its benchmarks. The library's comprehensive dictionary is generated from `mime-db`, which aggregates IANA, NGINX, and Apache datasets, ensuring accuracy for standard MIME types while intentionally omitting experimental and vendor-specific entries to maintain its lightweight nature. It supports both native ESM and CommonJS environments, including Deno, and allows for dictionary customization. The project maintains an active release cadence, primarily syncing with `mime-db` updates and addressing minor breaking changes between major versions.

serialization

npm install mrmime

github ↗package ↗

INSTALL

IMPORT

SIG · MRMIME

mrmime

serializationjavascriptv0.0.1

Install

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Import

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Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

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glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

lookup

✓ import { lookup } from 'mrmime';

✗ const lookup = require('mrmime').lookup;

Primarily designed for ESM. While CommonJS works, named imports are preferred.

mimes

✓ import { mimes } from 'mrmime';

✗ const mimes = require('mrmime').mimes;

The `mimes` object allows for runtime additions or overrides of MIME types and is mutable.

mrmime (CommonJS destructuring)

✓ const { lookup, mimes } = require('mrmime');

For CommonJS environments, destructuring the require call is the idiomatic way to access named exports.

Demonstrates how to lookup MIME types for various inputs, handle unknown extensions, and dynamically customize the internal MIME dictionary.

import { lookup, mimes } from 'mrmime'; // Get a MIME type from an extension or filename console.log(lookup('txt')); // => "text/plain" console.log(lookup('.txt')); // => "text/plain" console.log(lookup('a.txt')); // => "text/plain" console.log(lookup('index.html')); // => "text/html" // Handle unknown extensions (returns undefined since v2.0.0) console.log(lookup('.xyz')); // => undefined // Customize the MIME dictionary by adding a new type mimes['xyz'] = 'hello/world'; console.log(lookup('xyz')); // => "hello/world" // Example with a common file type check const filename = 'document.pdf'; const mimeType = lookup(filename); if (mimeType) { console.log(`The MIME type for '${filename}' is: ${mimeType}`); } else { console.log(`Could not determine MIME type for '${filename}'.`); }

Debug

Known issues

breakingThe `lookup` function's return signature changed from `string | void` to `string | undefined` in v2.0.0. This aligns with TypeScript's `undefined` type for missing values.

fix

Update type assertions or nullish coalescing logic to explicitly check for `undefined` instead of `void`.

affects: >=2.0.0

breakingUpgrading to `mrmime` v2.0.0 includes an updated `mime-db` version, which resulted in changes to some extension-to-MIME-type mappings. Specifically, the `es` extension was removed, and others like `asc` had their values changed. Review the full changelog for details.

fix

Verify that expected MIME types for specific extensions are still correct after upgrading. If a previously recognized type is now `undefined` or changed, update application logic or manually add/override the type in the `mimes` dictionary.

affects: >=2.0.0

gotchaIn `mrmime` versions up to `v1.0.0`, TypeScript 4.7+ environments might not correctly discover the type definitions. This was fixed in `v1.0.1` by adding the 'types' export condition.

fix

Upgrade to `mrmime` v1.0.1 or newer to ensure correct TypeScript type discovery.

affects: <=1.0.0

Errors

Common errors & fixes

TypeError: (0 , mrmime_1.lookup) is not a function

Attempting to use CommonJS `require` with named imports incorrectly in an environment expecting ES modules, or vice-versa.

fix

If using `require`, use `const { lookup } = require('mrmime');`. If in an ES module environment, ensure `import { lookup } from 'mrmime';` is used and the file is treated as an ES module (e.g., `.mjs` extension or `type: 'module'` in `package.json`).

MIME type not found for '.xyz'

Looking up an extension that is not present in `mrmime`'s internal dictionary, which will result in `lookup` returning `undefined`.

fix

Recognize that `lookup` returns `undefined` for unknown extensions. If the extension is valid for your application, add it to the `mimes` dictionary: `mimes['xyz'] = 'your/custom-type';`.

Upgrade

Version history

0.0.1latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/lukeed/mrmime ↗

packagehttps://www.npmjs.com/package/mrmime ↗