MIME

MIME is a comprehensive library for MIME type mapping that enables developers to determine file types based on extensions and vice versa. It offers a complete database of MIME types (800+ types, 1,000+ extensions) with both full and lite versions, supports TypeScript with built-in type definitions, and provides both programmatic API and command-line interface.

Package Information

• Package Name: mime
• Package Type: npm
• Language: TypeScript
• Installation: npm install mime

Core Imports

import mime from "mime";
import { Mime } from "mime";

For lite version (without unofficial types):

import mime from "mime/lite";
import { Mime } from "mime/lite";

CommonJS (not recommended, use ESM):

const mime = require("mime");
const { Mime } = require("mime");

Basic Usage

import mime from "mime";

// Get MIME type from file path or extension
const type = mime.getType("script.js");           // "text/javascript"
const type2 = mime.getType("data.json");          // "application/json"

// Get default extension from MIME type
const ext = mime.getExtension("text/plain");      // "txt"
const ext2 = mime.getExtension("image/jpeg");     // "jpeg"

// Get all extensions for a MIME type (new in v4)
const extensions = mime.getAllExtensions("image/jpeg"); // Set(3) { "jpeg", "jpg", "jpe" }

Architecture

MIME is built around several key components:

• Immutable Default Instances: Pre-configured, frozen instances with comprehensive MIME type databases
• Custom Mutable Instances: Mime class allowing custom type definitions and modifications
• Type Database Variants: Full version (all types) and lite version (standard types only)
• ESM-First Design: Modern ES module architecture with TypeScript support
• Command-Line Interface: Built-in CLI for shell scripting and automation

Capabilities

MIME Type Resolution

Core functionality for resolving MIME types from file paths and extensions, with robust path handling and null-safe operations.

function getType(path: string): string | null;

MIME Type Operations

Custom MIME Instances

Create and configure custom MIME instances with your own type definitions, perfect for specialized applications or custom file types.

class Mime {
  constructor(...args: TypeMap[]);
  define(typeMap: TypeMap, force?: boolean): this;
  getType(path: string): string | null;
  getExtension(type: string): string | null;
  getAllExtensions(type: string): Set<string> | null;
}

type TypeMap = { [key: string]: string[] };

Custom MIME Instances

Command Line Interface

Shell interface for MIME type operations, supporting both type-to-extension and extension-to-type lookups.

mime script.js                    # Returns: text/javascript
mime -r image/jpeg               # Returns: jpeg

Command Line Interface

Type Definitions

type TypeMap = { [key: string]: string[] };

interface MimeInstance {
  getType(path: string): string | null;
  getExtension(type: string): string | null;
  getAllExtensions(type: string): Set<string> | null;
}