# README

filetype

Small and dependency free Go package to infer file and MIME type checking the magic numbers signature.

For SVG file type checking, see go-is-svg package. Python port: filetype.py.

Features

Supports a wide range of file types
Provides file extension and proper MIME type
File discovery by extension or MIME type
File discovery by class (image, video, audio...)
Provides a bunch of helpers and file matching shortcuts
Pluggable: add custom new types and matchers
Simple and semantic API
Blazing fast, even processing large files
Only first 262 bytes representing the max file header is required, so you can just pass a slice
Dependency free (just Go code, no C compilation needed)
Cross-platform file recognition

Installation

go get github.com/h2non/filetype

API

See Godoc reference.

Subpackages

Examples

Simple file type checking

package main

import (
  "fmt"
  "io/ioutil"

  "github.com/h2non/filetype"
)

func main() {
  buf, _ := ioutil.ReadFile("sample.jpg")

  kind, _ := filetype.Match(buf)
  if kind == filetype.Unknown {
    fmt.Println("Unknown file type")
    return
  }

  fmt.Printf("File type: %s. MIME: %s\n", kind.Extension, kind.MIME.Value)
}

Check type class

package main

import (
  "fmt"
  "io/ioutil"

  "github.com/h2non/filetype"
)

func main() {
  buf, _ := ioutil.ReadFile("sample.jpg")

  if filetype.IsImage(buf) {
    fmt.Println("File is an image")
  } else {
    fmt.Println("Not an image")
  }
}

Supported type

package main

import (
  "fmt"

  "github.com/h2non/filetype"
)

func main() {
  // Check if file is supported by extension
  if filetype.IsSupported("jpg") {
    fmt.Println("Extension supported")
  } else {
    fmt.Println("Extension not supported")
  }

  // Check if file is supported by extension
  if filetype.IsMIMESupported("image/jpeg") {
    fmt.Println("MIME type supported")
  } else {
    fmt.Println("MIME type not supported")
  }
}

File header

package main

import (
  "fmt"
  "io/ioutil"

  "github.com/h2non/filetype"
)

func main() {
  // Open a file descriptor
  file, _ := os.Open("movie.mp4")

  // We only have to pass the file header = first 261 bytes
  head := make([]byte, 261)
  file.Read(head)

  if filetype.IsImage(head) {
    fmt.Println("File is an image")
  } else {
    fmt.Println("Not an image")
  }
}

Add additional file type matchers

package main

import (
  "fmt"

  "github.com/h2non/filetype"
)

var fooType = filetype.NewType("foo", "foo/foo")

func fooMatcher(buf []byte) bool {
  return len(buf) > 1 && buf[0] == 0x01 && buf[1] == 0x02
}

func main() {
  // Register the new matcher and its type
  filetype.AddMatcher(fooType, fooMatcher)

  // Check if the new type is supported by extension
  if filetype.IsSupported("foo") {
    fmt.Println("New supported type: foo")
  }

  // Check if the new type is supported by MIME
  if filetype.IsMIMESupported("foo/foo") {
    fmt.Println("New supported MIME type: foo/foo")
  }

  // Try to match the file
  fooFile := []byte{0x01, 0x02}
  kind, _ := filetype.Match(fooFile)
  if kind == filetype.Unknown {
    fmt.Println("Unknown file type")
  } else {
    fmt.Printf("File type matched: %s\n", kind.Extension)
  }
}

Supported types

Image

jpg - image/jpeg
png - image/png
gif - image/gif
webp - image/webp
cr2 - image/x-canon-cr2
tif - image/tiff
bmp - image/bmp
heif - image/heif
jxr - image/vnd.ms-photo
psd - image/vnd.adobe.photoshop
ico - image/vnd.microsoft.icon
dwg - image/vnd.dwg

Video

mp4 - video/mp4
m4v - video/x-m4v
mkv - video/x-matroska
webm - video/webm
mov - video/quicktime
avi - video/x-msvideo
wmv - video/x-ms-wmv
mpg - video/mpeg
flv - video/x-flv
3gp - video/3gpp

Audio

mid - audio/midi
mp3 - audio/mpeg
m4a - audio/m4a
ogg - audio/ogg
flac - audio/x-flac
wav - audio/x-wav
amr - audio/amr
aac - audio/aac
aiff - audio/x-aiff

Documents

doc - application/msword
docx - application/vnd.openxmlformats-officedocument.wordprocessingml.document
xls - application/vnd.ms-excel
xlsx - application/vnd.openxmlformats-officedocument.spreadsheetml.sheet
ppt - application/vnd.ms-powerpoint
pptx - application/vnd.openxmlformats-officedocument.presentationml.presentation

Font

woff - application/font-woff
woff2 - application/font-woff
ttf - application/font-sfnt
otf - application/font-sfnt

Application

wasm - application/wasm
dex - application/vnd.android.dex
dey - application/vnd.android.dey

Benchmarks

Measured using real files.

Environment: OSX x64 i7 2.7 Ghz

BenchmarkMatchTar-8    1000000        1083 ns/op
BenchmarkMatchZip-8    1000000        1162 ns/op
BenchmarkMatchJpeg-8   1000000        1280 ns/op
BenchmarkMatchGif-8    1000000        1315 ns/op
BenchmarkMatchPng-8    1000000        1121 ns/op