diff --git a/config.go b/config.go
index dcf5ca0..22dc2d6 100644
--- a/config.go
+++ b/config.go
@@ -22,7 +22,7 @@ var (
 	prefetch, proxyMode      bool
 	remoteRaw                = "remote-raw"
 	config                   Config
-	version                  = "0.4.2"
+	version                  = "0.4.3"
 	releaseUrl               = "https://github.com/webp-sh/webp_server_go/releases/latest/download/"
 )
 
diff --git a/encoder.go b/encoder.go
index cebc20a..d6193da 100644
--- a/encoder.go
+++ b/encoder.go
@@ -4,10 +4,6 @@ import (
 	"bytes"
 	"errors"
 	"fmt"
-	"github.com/Kagami/go-avif"
-	"github.com/chai2010/webp"
-	log "github.com/sirupsen/logrus"
-	"golang.org/x/image/bmp"
 	"image"
 	"image/jpeg"
 	"image/png"
@@ -17,6 +13,11 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+
+	"github.com/Kagami/go-avif"
+	"github.com/chai2010/webp"
+	log "github.com/sirupsen/logrus"
+	"golang.org/x/image/bmp"
 )
 
 func convertFilter(raw, avifPath, webpPath string, c chan int) {
@@ -72,12 +73,12 @@ func readRawImage(imgPath string, maxPixel int) (img image.Image, err error) {
 		log.Errorln(err)
 	}
 
-	contentType := getFileContentType(data[:512])
-	if strings.Contains(contentType, "jpeg") {
+	imgExtension := strings.ToLower(path.Ext(imgPath))
+	if strings.Contains(imgExtension, "jpeg") || strings.Contains(imgExtension, "jpg") {
 		img, err = jpeg.Decode(bytes.NewReader(data))
-	} else if strings.Contains(contentType, "png") {
+	} else if strings.Contains(imgExtension, "png") {
 		img, err = png.Decode(bytes.NewReader(data))
-	} else if strings.Contains(contentType, "bmp") {
+	} else if strings.Contains(imgExtension, "bmp") {
 		img, err = bmp.Decode(bytes.NewReader(data))
 	}
 	if err != nil || img == nil {
diff --git a/helper.go b/helper.go
index d9e3130..5ef45fb 100644
--- a/helper.go
+++ b/helper.go
@@ -3,6 +3,7 @@ package main
 import (
 	"bytes"
 	"fmt"
+	"github.com/h2non/filetype"
 	"hash/crc32"
 	"io"
 	"io/ioutil"
@@ -16,7 +17,6 @@ import (
 
 	"strings"
 
-	"github.com/h2non/filetype"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -33,6 +33,7 @@ func avifMatcher(buf []byte) bool {
 	})
 }
 func getFileContentType(buffer []byte) string {
+	// TODO deprecated.
 	var avifType = filetype.NewType("avif", "image/avif")
 	filetype.AddMatcher(avifType, avifMatcher)
 	kind, _ := filetype.Match(buffer)
@@ -127,7 +128,7 @@ func cleanProxyCache(cacheImagePath string) {
 	}
 }
 
-func genOptimizedAbs(rawImagePath string, exhaustPath string, imageName string, reqURI string) (string, string) {
+func genOptimizedAbsPath(rawImagePath string, exhaustPath string, imageName string, reqURI string) (string, string) {
 	// get file mod time
 	STAT, err := os.Stat(rawImagePath)
 	if err != nil {
diff --git a/helper_test.go b/helper_test.go
index 9217e8a..73144b1 100644
--- a/helper_test.go
+++ b/helper_test.go
@@ -45,7 +45,7 @@ func TestImageExists(t *testing.T) {
 }
 
 func TestGenWebpAbs(t *testing.T) {
-	cwd, cooked := genOptimizedAbs("./pics/webp_server.png", "/tmp",
+	cwd, cooked := genOptimizedAbsPath("./pics/webp_server.png", "/tmp",
 		"test", "a")
 	if !strings.Contains(cwd, "webp_server_go") {
 		t.Logf("Result: [%v], Expected: [%v]", cwd, "webp_server_go")
diff --git a/prefetch.go b/prefetch.go
index 1dbca1d..654b29e 100644
--- a/prefetch.go
+++ b/prefetch.go
@@ -2,13 +2,14 @@ package main
 
 import (
 	"fmt"
-	"github.com/schollz/progressbar/v3"
-	log "github.com/sirupsen/logrus"
 	"os"
 	"path"
 	"path/filepath"
 	"strings"
 	"time"
+
+	"github.com/schollz/progressbar/v3"
+	log "github.com/sirupsen/logrus"
 )
 
 func prefetchImages(confImgPath string, ExhaustPath string) {
@@ -33,7 +34,7 @@ func prefetchImages(confImgPath string, ExhaustPath string) {
 			}
 			// RawImagePath string, ImgFilename string, reqURI string
 			proposedURI := strings.Replace(picAbsPath, confImgPath, "", 1)
-			avif, webp := genOptimizedAbs(picAbsPath, ExhaustPath, info.Name(), proposedURI)
+			avif, webp := genOptimizedAbsPath(picAbsPath, ExhaustPath, info.Name(), proposedURI)
 			_ = os.MkdirAll(path.Dir(avif), 0755)
 			log.Infof("Prefetching %s", picAbsPath)
 			go convertFilter(picAbsPath, avif, webp, finishChan)
diff --git a/router.go b/router.go
index 5e09b4d..8e08a55 100644
--- a/router.go
+++ b/router.go
@@ -3,7 +3,6 @@ package main
 import (
 	"errors"
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"net/url"
 	"os"
@@ -65,7 +64,7 @@ func convert(c *fiber.Ctx) error {
 	}
 
 	// generate with timestamp to make sure files are update-to-date
-	avifAbs, webpAbs := genOptimizedAbs(rawImageAbs, config.ExhaustPath, imgFilename, reqURI)
+	avifAbs, webpAbs := genOptimizedAbsPath(rawImageAbs, config.ExhaustPath, imgFilename, reqURI)
 	convertFilter(rawImageAbs, avifAbs, webpAbs, nil)
 
 	var availableFiles = []string{rawImageAbs}
@@ -78,14 +77,18 @@ func convert(c *fiber.Ctx) error {
 		}
 	}
 
-	var finalFile = findSmallestFiles(availableFiles)
-	etag := genEtag(finalFile)
-	c.Set("ETag", etag)
-	c.Set("X-Compression-Rate", getCompressionRate(rawImageAbs, finalFile))
-	buf, _ := ioutil.ReadFile(finalFile)
-	c.Set("content-type", getFileContentType(buf))
-	return c.SendFile(finalFile)
+	var finalFileName = findSmallestFiles(availableFiles)
+	var finalFileExtension = path.Ext(finalFileName)
+	if finalFileExtension == ".webp" {
+		c.Set("Content-Type", "image/webp")
+	} else if finalFileExtension == ".avif" {
+		c.Set("Content-Type", "image/avif")
+	}
 
+	etag := genEtag(finalFileName)
+	c.Set("ETag", etag)
+	c.Set("X-Compression-Rate", getCompressionRate(rawImageAbs, finalFileName))
+	return c.SendFile(finalFileName)
 }
 
 func proxyHandler(c *fiber.Ctx, reqURI string) error {