diff --git a/kadai3/imura81gt/rget/cmd/rget/main_test.go b/kadai3/imura81gt/rget/cmd/rget/main_test.go
new file mode 100644
index 0000000..097f27a
--- /dev/null
+++ b/kadai3/imura81gt/rget/cmd/rget/main_test.go
@@ -0,0 +1,5 @@
+package main
+
+import "testing"
+
+func TestMain(t *testing.T) {}
diff --git a/kadai3/imura81gt/rget/rget.go b/kadai3/imura81gt/rget/rget.go
index 974b904..4f3adcb 100644
--- a/kadai3/imura81gt/rget/rget.go
+++ b/kadai3/imura81gt/rget/rget.go
@@ -40,7 +40,7 @@ type Units []Unit
 
 func Run(option Option) {
 	fmt.Printf("%+v\n", option)
-	err := option.contentLength()
+	err := option.checkingHeaders()
 	if err != nil {
 		fmt.Errorf("%s", err)
 	}
@@ -66,8 +66,7 @@ func Run(option Option) {
 
 }
 
-func (o *Option) contentLength() error {
-	//resp, err := http.Head(url)
+func (o *Option) checkingHeaders() error {
 	resp, err := http.Head(o.URL)
 	if err != nil {
 		return err
@@ -77,20 +76,51 @@ func (o *Option) contentLength() error {
 		err := fmt.Errorf("%s URL cannot support Ranges Requests", o.URL)
 		return err
 	}
+
 	if resp.Header["Accept-Ranges"][0] == "none" {
 		err := fmt.Errorf("%s cannot support Ranges Requests", o.URL)
 		return err
 	}
+
 	if resp.ContentLength == 0 {
 		err := fmt.Errorf("%s size is %s", o.URL, resp.Header["Content-Length"][0])
 		return err
 	}
 
+	redirectURL := resp.Request.URL.String()
+	if err != nil {
+		return err
+	}
+
 	o.ContentLength = resp.ContentLength
-	//return resp.ContentLength, nil
+
+	// keep the redirect URL that accept Ranges Requests because some mirror sites may deny.
+	// TODO: redirectURL should set by Unit separately.
+	if o.URL != redirectURL {
+		o.URL = redirectURL
+	}
+
 	return err
 }
 
+func (o *Option) acceptRangesHeaderCheck() (string, error) {
+	resp, err := http.Head(o.URL)
+	redirectURL := resp.Request.URL.String()
+	if err != nil {
+		return redirectURL, err
+	}
+
+	if resp.Header.Get("Accept-Ranges") == "" {
+		err := fmt.Errorf("%s URL cannot support Ranges Requests", o.URL)
+		return redirectURL, err
+	}
+	if resp.Header["Accept-Ranges"][0] == "none" {
+		err := fmt.Errorf("%s cannot support Ranges Requests", o.URL)
+		return redirectURL, err
+	}
+	return redirectURL, nil
+}
+
 //func divide(contentLength int64, concurrency int) Units {
 func (o *Option) divide() {
 	var units []Unit
@@ -161,6 +191,8 @@ func (o *Option) downloadWithContext(
 	req.Header.Set("Range", byteRange)
 
 	client := http.DefaultClient
+	// TODO: should check resp.StatusCode.
+	//   client.Do cannot seems to return the err when statusCode is 50x etc.
 	resp, err := client.Do(req)
 	if err != nil {
 		fmt.Printf("client err: %s", err)