diff --git a/frontend/packages/core/src/utils/fetch.ts b/frontend/packages/core/src/utils/fetch.ts
index 244ff0a195a2308d0d5fca7e6f502338a2453f97..b48b684a4d307a0efc447cbca976ae141a24d324 100644
--- a/frontend/packages/core/src/utils/fetch.ts
+++ b/frontend/packages/core/src/utils/fetch.ts
@@ -80,44 +80,50 @@ export async function fetcher<T = unknown>(url: string, options?: RequestInit):
     }
 
     let response: Data<T> | T;
-    try {
-        if (res.headers.get('content-type')?.includes('application/json')) {
+    if (res.headers.get('content-type')?.includes('application/json')) {
+        try {
             response = await res.json();
-            if (response && 'status' in response) {
-                if (response.status !== 0) {
-                    const t = await logErrorAndReturnT(response);
-                    throw new Error((response as ErrorData).msg || t('errors:error'));
-                } else {
-                    return (response as SuccessData<T>).data;
-                }
-            }
-            return response;
-        } else {
-            const data = await res.blob();
-            const disposition = res.headers.get('Content-Disposition');
-            // support safari
-            if (!data.arrayBuffer) {
-                data.arrayBuffer = async () =>
-                    new Promise<ArrayBuffer>((resolve, reject) => {
-                        const fileReader = new FileReader();
-                        fileReader.addEventListener('load', e =>
-                            e.target ? resolve(e.target.result as ArrayBuffer) : reject()
-                        );
-                        fileReader.readAsArrayBuffer(data);
-                    });
+        } catch (e) {
+            const t = await logErrorAndReturnT(e);
+            throw new Error(t('errors:parse-error'));
+        }
+        if (response && 'status' in response) {
+            if (response.status !== 0) {
+                const t = await logErrorAndReturnT(response);
+                throw new Error((response as ErrorData).msg || t('errors:error'));
+            } else {
+                return (response as SuccessData<T>).data;
             }
-            let filename: string | null = null;
-            if (disposition && disposition.indexOf('attachment') !== -1) {
-                const matches = /filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/.exec(disposition);
-                if (matches != null && matches[1]) {
-                    filename = matches[1].replace(/['"]/g, '');
-                }
+        }
+        return response;
+    } else {
+        let data: Blob;
+        try {
+            data = await res.blob();
+        } catch (e) {
+            const t = await logErrorAndReturnT(e);
+            throw new Error(t('errors:parse-error'));
+        }
+        const disposition = res.headers.get('Content-Disposition');
+        // support safari
+        if (!data.arrayBuffer) {
+            data.arrayBuffer = async () =>
+                new Promise<ArrayBuffer>((resolve, reject) => {
+                    const fileReader = new FileReader();
+                    fileReader.addEventListener('load', e =>
+                        e.target ? resolve(e.target.result as ArrayBuffer) : reject()
+                    );
+                    fileReader.readAsArrayBuffer(data);
+                });
+        }
+        let filename: string | null = null;
+        if (disposition && disposition.indexOf('attachment') !== -1) {
+            const matches = /filename[^;=\n]*=((['"]).*?\2|[^;\n]*)/.exec(disposition);
+            if (matches != null && matches[1]) {
+                filename = matches[1].replace(/['"]/g, '');
             }
-            return {data, type: res.headers.get('Content-Type'), filename};
         }
-    } catch (e) {
-        const t = await logErrorAndReturnT(e);
-        throw new Error(t('errors:parse-error'));
+        return {data, type: res.headers.get('Content-Type'), filename};
     }
 }
 
diff --git a/visualdl/server/app.py b/visualdl/server/app.py
index 29ae6d26e9ffc82984d51074e8dd89145a94ea8b..ab939814e924ee7f72fb1aee86306333d5022e11 100644
--- a/visualdl/server/app.py
+++ b/visualdl/server/app.py
@@ -69,6 +69,12 @@ def create_app(args):
     public_path = args.public_path
     api_path = public_path + '/api'
 
+    def append_query_string(url):
+        query_string = ''
+        if request.query_string:
+            query_string = '?' + request.query_string.decode()
+        return url + query_string
+
     @babel.localeselector
     def get_locale():
         lang = args.language
@@ -87,7 +93,7 @@ def create_app(args):
 
         @app.route('/')
         def base():
-            return redirect(public_path, code=302)
+            return redirect(append_query_string(public_path), code=302)
 
         @app.route('/favicon.ico')
         def favicon():
@@ -98,10 +104,7 @@ def create_app(args):
 
         @app.route(public_path + '/')
         def index():
-            query_string = ''
-            if request.query_string:
-                query_string = '?' + request.query_string.decode()
-            return redirect(public_path + '/index' + query_string, code=302)
+            return redirect(append_query_string(public_path + '/index'), code=302)
 
         @app.route(public_path + '/<path:filename>')
         def serve_static(filename):