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• About
• Status
• Related packages
• Installation
• Dependencies
• Usage examples
• API
  • Determining MIME type from file extension
  • Determining file extension from MIME type
  • Checking if MIME type is compressible
• Conversion from mime-db
• Authors
• License

About

650+ file extension to MIME type mappings, based on mime-db.

All MIME type mappings are based on mime-db (2023-02-17). For filesize reasons only a small selected number of vendor MIME types (aka */vnd.*) are included. Most of the omitted ones are fairly obscure anyway, so likely not problematic...

Additionally, this package defines some MIME types not included in the original DB, as well as some preference overrides.

Status

STABLE - used in production

Search or submit any issues for this package

Related packages

• @thi.ng/dl-asset - Canvas, video recording & file asset download helpers for web apps

Installation

yarn add @thi.ng/mime

ESM import:

import * as mime from "@thi.ng/mime";

Browser ESM import:

<script type="module" src="https://esm.run/@thi.ng/mime"></script>

JSDelivr documentation

For Node.js REPL:

const mime = await import("@thi.ng/mime");

Package sizes (brotli'd, pre-treeshake): ESM: 4.83 KB

Dependencies

None

Usage examples

Eight projects in this repo's /examples directory are using this package:

| Screenshot | Description | Live demo | Source | |:---------------------------------------------------------------------------------------------------------------------------|:----------------------------------------------------------------------------|:----------------------------------------------------------|:---------------------------------------------------------------------------------------| | | Interactive image processing (adaptive threshold) | Demo | Source | | | Interactive & reactive image blurhash generator | Demo | Source | | | Color palette generation via dominant color extraction from uploaded images | Demo | Source | | | Interactive pixel sorting tool using thi.ng/color & thi.ng/pixel | Demo | Source | | | RGB waveform image analysis | Demo | Source | | | Basic usage of the declarative rdom-forms generator | Demo | Source | | | Multi-layer vectorization & dithering of bitmap images | Demo | Source | | | rdom & WebGL-based image channel editor | Demo | Source |

API

Generated API docs

This package exposes a MIME_TYPES object which provides mappings from file extensions to MIME types. For each extension one or more MIME types are provided, with the default type always in first position.

import { MIME_TYPES } from "@thi.ng/mime";

MIME_TYPES.mp3
// [ 'audio/mpeg', 'audio/mp3' ]

MIME_TYPES.jpg
// [ 'image/jpeg' ]

MIME_TYPES.jpeg
// [ 'image/jpeg' ]

Determining MIME type from file extension

To simplify lookup and support a fallback type, the package has preferredType() function:

import { preferredType } from "@thi.ng/mime";

preferredType("mp3")
// "audio/mpeg"

// unknown file extension w/ default fallback type
preferredType("foo")
// "application/octet-stream"

// unknown file extension w/ given fallback type
preferredType("foo", "text/plain")
// "text/plain"

Determining file extension from MIME type

Reverse lookups are possible too, using preferredExtension() (also supports fallback):

import { preferredExtension } from "@thi.ng/mime";

preferredExtension("image/svg+xml");
// "svg"

preferredExtension("image/foo");
// "bin" (default fallback)

preferredExtension("image/foo", "dat");
// "dat" (custom fallback)

Checking if MIME type is compressible

The original mime-db includes information if a MIME type is compressible (gzippable). This information can be obtained via isCompressible(). Note: Some of these decisions seem to be questionable/wrong (e.g. many plain text formats are marked as false), but taken here as provided...

import { isCompressible } from "@thi.ng/mime";

isCompressible("text/javascript");
// true

isCompressible(preferredType("mp4"))
// false

Conversion from mime-db

1. Download the latest version of mime-db's JSON index and save it to [packages/mime/]tools/mime-db.json
2. Run the following command to build an up-to-date index (assumes the umbrella repo has been pre-built already). Output will always be be written to src/generated.ts.

# from the thi.ng/umbrella repo root
(cd packages/mime && yarn tool:convert)

Additional configuration options are available in the tools/convert.ts script.

Authors

• Karsten Schmidt

If this project contributes to an academic publication, please cite it as:

@misc{thing-mime,
  title = "@thi.ng/mime",
  author = "Karsten Schmidt",
  note = "https://thi.ng/mime",
  year = 2020
}

License

© 2020 - 2025 Karsten Schmidt // Apache License 2.0