mime-detector
A TypeScript module that accurately detects file MIME types by examining both file contents (magic bytes) and extensions.
Features
- Accurate file type detection using magic bytes (file signatures)
- Fallback to extension-based detection when magic bytes aren't conclusive
- Support for common document, image, audio, and video formats
- Written in TypeScript with full type definitions
- Zero runtime dependencies
Installation
npm install mime-detector
Usage
import { getMimeType, getMimeExtension, isDocument, isImage, isAudio, isVideo } from 'mime-detector';
// Get MIME type
console.log(await getMimeType('https://example.com/document.pdf')); // 'application/pdf'
console.log(await getMimeType('https://example.com/image.jpg')); // 'image/jpeg'
// Get file extension from MIME type
console.log(getMimeExtension('image/jpeg')); // '.jpg'
console.log(getMimeExtension('application/pdf')); // '.pdf'
// Check file type
console.log(await isDocument('https://example.com/document.pdf')); // true
console.log(await isImage('https://example.com/image.jpg')); // true
console.log(await isAudio('https://example.com/song.mp3')); // true
console.log(await isVideo('https://example.com/movie.mp4')); // true
API
getMimeType(filePath: string): Promise
Returns the MIME type for the given file path. First attempts to detect the type by reading the file's magic bytes, then falls back to extension-based detection if necessary.
getMimeExtension(mimeType: string): string | null
Returns the corresponding file extension (including the dot) for a given MIME type. Returns null if no matching extension is found.
Helper Functions
isDocument(filePath: string): Promise<boolean> - Checks if the file is a documentisImage(filePath: string): Promise<boolean> - Checks if the file is an imageisAudio(filePath: string): Promise<boolean> - Checks if the file is an audio fileisVideo(filePath: string): Promise<boolean> - Checks if the file is a video file
Supported Formats
Documents
- PDF (.pdf)
- Microsoft Word (.doc, .docx)
- Text (.txt)
- Rich Text Format (.rtf)
Images
- JPEG (.jpg, .jpeg)
- PNG (.png)
- GIF (.gif)
- WebP (.webp)
- SVG (.svg)
Audio
- MP3 (.mp3)
- WAV (.wav)
- OGG (.ogg)
- M4A (.m4a)
Video
- MP4 (.mp4)
- WebM (.webm)
- AVI (.avi)
- QuickTime (.mov)
- Matroska (.mkv)
Magic Bytes Detection
The module first attempts to detect file types by examining their magic bytes (file signatures). This provides more accurate detection than extension-based methods alone, as it looks at the actual file contents. Currently supports magic bytes detection for:
- PDF files
- JPEG images
- PNG images
- GIF images
- MP3 audio
- MP4 video
- WebM video
For other formats, or when magic bytes detection fails, the module falls back to extension-based detection.
Error Handling
If the file cannot be read (e.g., due to permissions or if it doesn't exist), the module falls back to extension-based detection. If the file type cannot be determined, it returns 'application/octet-stream'.
License
MIT
Contributing
Contributions are welcome! Feel free to submit issues and pull requests.
Some areas where you could help:
- Adding support for more file formats
- Adding more magic byte signatures
- Improving detection accuracy
- Adding tests
- Documentation improvements
