diff --git a/docker-compose.dev.yml b/docker-compose.dev.yml
index fae06b8f..ca08d249 100644
--- a/docker-compose.dev.yml
+++ b/docker-compose.dev.yml
@@ -21,6 +21,7 @@ services:
     environment:
       IMGPROXY_KEY: ${READFLOW_HASH_SECRET_KEY:-736563726574}
       IMGPROXY_SALT: ${READFLOW_HASH_SECRET_SALT:-706570706572} 
+      IMGPROXY_ENABLE_WEBP_DETECTION: true 
     ports:
       - "${IMAGOR_PORT:-8081}:8080"
   #######################################
diff --git a/docker-compose.yml b/docker-compose.yml
index f9a0dbd3..d07ac1a7 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -21,7 +21,8 @@ services:
     image: darthsim/imgproxy
     environment:
       IMGPROXY_KEY: ${READFLOW_HASH_SECRET_KEY:-736563726574}
-      IMGPROXY_SALT: ${READFLOW_HASH_SECRET_SALT:-706570706572} 
+      IMGPROXY_SALT: ${READFLOW_HASH_SECRET_SALT:-706570706572}
+      IMGPROXY_ENABLE_WEBP_DETECTION: true 
     logging:
       driver: "json-file"
       options:
diff --git a/pkg/api/image-proxy.go b/pkg/api/image-proxy.go
index ebfbedef..134c5d0c 100644
--- a/pkg/api/image-proxy.go
+++ b/pkg/api/image-proxy.go
@@ -8,10 +8,9 @@ import (
 
 	"github.com/ncarlier/readflow/pkg/config"
 	"github.com/ncarlier/readflow/pkg/constant"
+	"github.com/ncarlier/readflow/pkg/helper"
 )
 
-const defaultUserAgent = "Mozilla/5.0 (X11; Linux x86_64; rv:10.0) Gecko/20100101 Firefox/10.0"
-
 var hopHeaders = []string{
 	"Connection",
 	"Keep-Alive",
@@ -26,7 +25,11 @@ var hopHeaders = []string{
 func copyHeader(dst, src http.Header) {
 	for k, vv := range src {
 		for _, v := range vv {
-			dst.Add(k, v)
+			if dst.Get(k) != "" {
+				dst.Set(k, v)
+			} else {
+				dst.Add(k, v)
+			}
 		}
 	}
 }
@@ -71,16 +74,12 @@ func imgProxyHandler(conf *config.Config) http.Handler {
 			return
 		}
 
-		// Manage request headers
-		userAgent := r.Header.Get("User-Agent")
-		if userAgent == "" {
-			userAgent = defaultUserAgent
-		}
-		req.Header.Set("User-Agent", userAgent)
+		// Manage request headers: copy, add x-forward, del hop
+		copyHeader(req.Header, r.Header)
 		if clientIP, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
 			appendHostToXForwardHeader(req.Header, clientIP)
 		}
-		delHopHeaders(r.Header)
+		delHopHeaders(req.Header)
 
 		// Do proxy request
 		resp, err := constant.DefaultClient.Do(req)
@@ -90,6 +89,17 @@ func imgProxyHandler(conf *config.Config) http.Handler {
 		}
 		defer resp.Body.Close()
 
+		// Redirect if image proxy failed
+		if resp.StatusCode >= 400 {
+			// decode image URL from proxy path
+			if img, err := helper.DecodeImageProxyPath(path); err != nil {
+				http.Error(w, err.Error(), http.StatusBadGateway)
+			} else {
+				http.Redirect(w, r, string(img), http.StatusTemporaryRedirect)
+			}
+			return
+		}
+
 		// Create proxy response
 		delHopHeaders(resp.Header)
 		copyHeader(w.Header(), resp.Header)
diff --git a/pkg/helper/image-proxy.go b/pkg/helper/image-proxy.go
new file mode 100644
index 00000000..7f17a472
--- /dev/null
+++ b/pkg/helper/image-proxy.go
@@ -0,0 +1,23 @@
+package helper
+
+import (
+	"encoding/base64"
+	"strings"
+)
+
+// Encode image URL to Image Proxy path
+func EncodeImageProxyPath(url, size string) string {
+	return "/resize:fit:" + size + "/" + base64.StdEncoding.EncodeToString([]byte(url))
+}
+
+// Decode image URL from Image Proxy Path
+func DecodeImageProxyPath(path string) (url string, err error) {
+	url = path[strings.LastIndex(path, "/")+1:]
+	var decoded []byte
+	decoded, err = base64.StdEncoding.DecodeString(url)
+	if err == nil {
+		url = string(decoded)
+	}
+
+	return
+}
diff --git a/pkg/helper/sign.go b/pkg/helper/sign.go
deleted file mode 100644
index f0e8adb8..00000000
--- a/pkg/helper/sign.go
+++ /dev/null
@@ -1,18 +0,0 @@
-package helper
-
-import (
-	"crypto/hmac"
-	"encoding/base64"
-	"hash"
-)
-
-// Sign value with secret
-func Sign(algo func() hash.Hash, value, secret string, truncate int) string {
-	h := hmac.New(algo, []byte(secret))
-	h.Write([]byte(value))
-	sig := base64.URLEncoding.EncodeToString(h.Sum(nil))
-	if truncate > 0 && len(sig) > truncate {
-		return sig[:truncate]
-	}
-	return sig
-}
diff --git a/pkg/service/articles_thumbnail.go b/pkg/service/articles_thumbnail.go
index 1ba0dd1b..71c519d4 100644
--- a/pkg/service/articles_thumbnail.go
+++ b/pkg/service/articles_thumbnail.go
@@ -5,6 +5,7 @@ import (
 	"crypto/sha256"
 	"encoding/base64"
 
+	"github.com/ncarlier/readflow/pkg/helper"
 	"github.com/ncarlier/readflow/pkg/model"
 )
 
@@ -13,7 +14,7 @@ func (reg *Registry) GetArticleThumbnailHash(article *model.Article, size string
 	if article.Image == nil || *article.Image == "" {
 		return ""
 	}
-	path := "/resize:fit:" + size + "/" + base64.StdEncoding.EncodeToString([]byte(*article.Image))
+	path := helper.EncodeImageProxyPath(*article.Image, size)
 
 	mac := hmac.New(sha256.New, reg.conf.Hash.SecretKey.Value)
 	mac.Write(reg.conf.Hash.SecretSalt.Value)