diff --git a/configs/dev.yml b/configs/dev.yml
index d3e66f2..8a2d5a0 100644
--- a/configs/dev.yml
+++ b/configs/dev.yml
@@ -8,7 +8,7 @@ server:
   debug: true
   host: "127.0.0.1"
   port: 8686
-  readTimeout: 2000
+  readTimeout: 4000
   writerTimeout: 86400000 # 1 day
   maxHeaderBytes: 512
   publicPath: "public"
diff --git a/public/static/css/style.css b/public/static/css/style.css
index 8a6e609..788604c 100644
--- a/public/static/css/style.css
+++ b/public/static/css/style.css
@@ -725,3 +725,9 @@ div.hr {
   overflow-wrap: break-word;
   display: block;
 }
+
+.alert-red {
+  border: dashed 1px #e74c3c;
+  color: #e74c3c;
+  border-radius: 0.5rem;
+}
\ No newline at end of file
diff --git a/src/client/web/src/components/browser.tsx b/src/client/web/src/components/browser.tsx
index 3184b36..91472ee 100644
--- a/src/client/web/src/components/browser.tsx
+++ b/src/client/web/src/components/browser.tsx
@@ -33,7 +33,7 @@ export interface BrowserProps {
   dirPath: List<string>;
   isSharing: boolean;
   items: List<MetadataResp>;
-  uploadings: List<UploadInfo>;
+  uploadings: List<UploadEntry>;
   sharings: List<string>;
 
   uploadFiles: List<File>;
@@ -328,9 +328,8 @@ export class Browser extends React.Component<Props, State, {}> {
       }
     );
 
-    const nameCellClass = `item-name item-name-${
-      this.props.browser.isVertical ? "vertical" : "horizontal"
-    } pointer`;
+    const nameCellClass = `item-name item-name-${this.props.browser.isVertical ? "vertical" : "horizontal"
+      } pointer`;
     const sizeCellClass = this.props.browser.isVertical
       ? `hidden margin-s`
       : ``;
@@ -422,9 +421,8 @@ export class Browser extends React.Component<Props, State, {}> {
             <span className="padding-m">
               <button
                 onClick={() => this.select(item.name)}
-                className={`${
-                  isSelected ? "blue0-bg white-font" : "grey2-bg grey3-font"
-                }`}
+                className={`${isSelected ? "blue0-bg white-font" : "grey2-bg grey3-font"
+                  }`}
                 style={{ width: "8rem", display: "inline-block" }}
               >
                 {isSelected
@@ -470,9 +468,8 @@ export class Browser extends React.Component<Props, State, {}> {
               <button
                 type="button"
                 onClick={() => this.select(item.name)}
-                className={`${
-                  isSelected ? "blue0-bg white-font" : "grey2-bg grey3-font"
-                }`}
+                className={`${isSelected ? "blue0-bg white-font" : "grey2-bg grey3-font"
+                  }`}
                 style={{ width: "8rem", display: "inline-block" }}
               >
                 {isSelected
@@ -593,50 +590,58 @@ export class Browser extends React.Component<Props, State, {}> {
       ) : null;
 
     const uploadingList = this.props.browser.uploadings.map(
-      (uploading: UploadInfo) => {
-        const pathParts = uploading.realFilePath.split("/");
+      (uploading: UploadEntry) => {
+        const pathParts = uploading.filePath.split("/");
         const fileName = pathParts[pathParts.length - 1];
 
         return (
-          <Flexbox
-            key={uploading.realFilePath}
-            children={List([
-              <span className="padding-m">
-                <Flexbox
-                  children={List([
-                    <RiUploadCloudLine
-                      size="3rem"
-                      className="margin-r-m blue0-font"
-                    />,
+          <div key={uploading.filePath}>
+            <Flexbox
+              children={List([
+                <span className="padding-m">
+                  <Flexbox
+                    children={List([
+                      <RiUploadCloudLine
+                        size="3rem"
+                        className="margin-r-m blue0-font"
+                      />,
 
-                    <div className={`${nameCellClass}`}>
-                      <span className="title-m">{fileName}</span>
-                      <div className="desc-m grey0-font">
-                        {FileSize(uploading.uploaded, { round: 0 })}
-                        &nbsp;/&nbsp;{FileSize(uploading.size, { round: 0 })}
-                      </div>
-                    </div>,
-                  ])}
-                />
-              </span>,
+                      <div className={`${nameCellClass}`}>
+                        <span className="title-m">{fileName}</span>
+                        <div className="desc-m grey0-font">
+                          {FileSize(uploading.uploaded, { round: 0 })}
+                          &nbsp;/&nbsp;{FileSize(uploading.size, { round: 0 })}
+                        </div>
+                      </div>,
+                    ])}
+                  />
+                </span>,
 
-              <div className="item-op padding-m">
-                <button
-                  onClick={() => this.stopUploading(uploading.realFilePath)}
-                  className="grey3-bg grey4-font margin-r-m"
-                >
-                  {this.props.msg.pkg.get("browser.stop")}
-                </button>
-                <button
-                  onClick={() => this.deleteUpload(uploading.realFilePath)}
-                  className="grey3-bg grey4-font"
-                >
-                  {this.props.msg.pkg.get("browser.delete")}
-                </button>
-              </div>,
-            ])}
-            childrenStyles={List([{}, { justifyContent: "flex-end" }])}
-          />
+                <div className="item-op padding-m">
+                  <button
+                    onClick={() => this.stopUploading(uploading.filePath)}
+                    className="grey3-bg grey4-font margin-r-m"
+                  >
+                    {this.props.msg.pkg.get("browser.stop")}
+                  </button>
+                  <button
+                    onClick={() => this.deleteUpload(uploading.filePath)}
+                    className="grey3-bg grey4-font"
+                  >
+                    {this.props.msg.pkg.get("browser.delete")}
+                  </button>
+                </div>,
+              ])}
+              childrenStyles={List([{}, { justifyContent: "flex-end" }])}
+            />
+            {uploading.err.trim() === "" ? null : (
+              <div className="alert-red margin-s">
+                <span className="padding-m">
+                  {uploading.err.trim()}
+                </span>
+              </div>
+            )}
+          </div>
         );
       }
     );
@@ -668,7 +673,7 @@ export class Browser extends React.Component<Props, State, {}> {
             />
           </div>
         ) : (
-          <div className="container">
+          <div className="container padding-b-m">
             <Flexbox
               children={List([
                 <span className="padding-m">
@@ -721,9 +726,8 @@ export class Browser extends React.Component<Props, State, {}> {
                   type="text"
                   readOnly
                   className="margin-r-m"
-                  value={`${
-                    document.location.href.split("?")[0]
-                  }?dir=${encodeURIComponent(dirPath)}`}
+                  value={`${document.location.href.split("?")[0]
+                    }?dir=${encodeURIComponent(dirPath)}`}
                 />
                 <button
                   onClick={() => {
diff --git a/src/client/web/src/components/core_state.ts b/src/client/web/src/components/core_state.ts
index 4a9b790..5bc2b01 100644
--- a/src/client/web/src/components/core_state.ts
+++ b/src/client/web/src/components/core_state.ts
@@ -2,6 +2,7 @@ import { List, Set, Map } from "immutable";
 
 import BgWorker from "../worker/upload.bg.worker";
 import { FgWorker } from "../worker/upload.fg.worker";
+import { UploadEntry } from "../worker/interface";
 
 import { BrowserProps } from "./browser";
 import { PanesProps } from "./panes";
@@ -9,8 +10,7 @@ import { LoginProps } from "./pane_login";
 import { AdminProps } from "./pane_admin";
 
 import { MsgPackage } from "../i18n/msger";
-import { Item } from "./browser";
-import { UploadInfo, User, MetadataResp } from "../client";
+import { User, MetadataResp } from "../client";
 import { initUploadMgr, IWorker } from "../worker/upload_mgr";
 
 export interface MsgProps {
@@ -56,7 +56,7 @@ export function initState(): ICoreState {
       items: List<MetadataResp>([]),
       sharings: List<string>([]),
       isSharing: false,
-      uploadings: List<UploadInfo>([]),
+      uploadings: List<UploadEntry>([]),
       uploadValue: "",
       uploadFiles: List<File>([]),
       tab: "",
diff --git a/src/client/web/src/components/state_updater.ts b/src/client/web/src/components/state_updater.ts
index 5ebf58b..377a6f7 100644
--- a/src/client/web/src/components/state_updater.ts
+++ b/src/client/web/src/components/state_updater.ts
@@ -39,7 +39,7 @@ export class Updater {
 
   initUploads = () => {
     this.props.browser.uploadings.forEach((entry) => {
-      Up().addStopped(entry.realFilePath, entry.uploaded, entry.size);
+      Up().addStopped(entry.filePath, entry.uploaded, entry.size);
     });
     // this.setUploadings(Up().list());
   };
@@ -63,13 +63,9 @@ export class Updater {
   };
 
   setUploadings = (infos: Map<string, UploadEntry>) => {
-    this.props.browser.uploadings = List<UploadInfo>(
-      infos.valueSeq().map((v: UploadEntry): UploadInfo => {
-        return {
-          realFilePath: v.filePath,
-          size: v.size,
-          uploaded: v.uploaded,
-        };
+    this.props.browser.uploadings = List<UploadEntry>(
+      infos.valueSeq().map((entry: UploadEntry): UploadEntry => {
+        return entry;
       })
     );
   };
@@ -105,13 +101,40 @@ export class Updater {
   };
 
   refreshUploadings = async (): Promise<boolean> => {
+    // this function get information from server and merge them with local information
+    // because some information (error) can only be detected from local
     const luResp = await this.filesClient.listUploadings();
+    if (luResp.status !== 200) {
+      // TODO: i18n
+      console.error(luResp.data);
+      return false;
+    }
 
-    this.props.browser.uploadings =
-      luResp.status === 200
-        ? List<UploadInfo>(luResp.data.uploadInfos)
-        : this.props.browser.uploadings;
-    return luResp.status === 200;
+    let remoteUploads = Map<string, UploadInfo>([]);
+    luResp.data.uploadInfos.forEach((info: UploadInfo) => {
+      remoteUploads = remoteUploads.set(info.realFilePath, info);
+    })
+
+    let updatedUploads = List<UploadEntry>([]);
+    this.props.browser.uploadings.forEach((localInfo: UploadEntry) => {
+      const remoteInfo = remoteUploads.get(localInfo.filePath);
+      if (remoteInfo == null) {
+        // TODO: i18n
+        localInfo.err = "not found in server";
+      } else {
+        updatedUploads.push({
+          file: localInfo.file,
+          filePath: localInfo.filePath,
+          size: remoteInfo.size,
+          uploaded: remoteInfo.uploaded,
+          state: localInfo.state,
+          err: localInfo.err,
+        });
+      }
+    });
+
+    this.props.browser.uploadings = updatedUploads;
+    return true;
   };
 
   stopUploading = (filePath: string) => {
diff --git a/src/client/web/src/worker/chunk_uploader.ts b/src/client/web/src/worker/chunk_uploader.ts
index c40240f..eb7beb4 100644
--- a/src/client/web/src/worker/chunk_uploader.ts
+++ b/src/client/web/src/worker/chunk_uploader.ts
@@ -6,7 +6,8 @@ import { UploadStatus, UploadState } from "./interface";
 // TODO: move chunk copying to worker
 const defaultChunkLen = 1024 * 1024 * 1;
 const speedDownRatio = 0.5;
-const speedUpRatio = 1.05;
+const speedUpRatio = 1.1;
+const speedLimit = 1024 * 1024 * 10; // 10MB
 const createRetryLimit = 2;
 const uploadRetryLimit = 1024;
 const backoffMax = 2000;
@@ -17,12 +18,11 @@ export interface ReaderResult {
 }
 
 export class ChunkUploader {
-  private reader = new FileReader();
   private client: IFilesClient = new FilesClient("");
 
   private chunkLen: number = defaultChunkLen;
 
-  constructor() {}
+  constructor() { }
 
   setClient = (client: IFilesClient) => {
     this.client = client;
@@ -70,6 +70,8 @@ export class ChunkUploader {
   ): Promise<UploadStatus> => {
     if (this.chunkLen === 0) {
       this.chunkLen = 1; // reset it to 1B
+    } else if (this.chunkLen > speedLimit) {
+      this.chunkLen = speedLimit;
     } else if (uploaded > file.size) {
       return {
         filePath,
@@ -79,13 +81,14 @@ export class ChunkUploader {
       };
     }
 
+    const reader = new FileReader();
     const readerPromise = new Promise<ReaderResult>(
       (resolve: (result: ReaderResult) => void) => {
-        this.reader.onerror = (_: ProgressEvent<FileReader>) => {
-          resolve({ err: this.reader.error });
+        reader.onerror = (_: ProgressEvent<FileReader>) => {
+          resolve({ err: reader.error });
         };
 
-        this.reader.onloadend = (ev: ProgressEvent<FileReader>) => {
+        reader.onloadend = (ev: ProgressEvent<FileReader>) => {
           const dataURL = ev.target.result as string; // readAsDataURL
           const base64Chunk = dataURL.slice(dataURL.indexOf(",") + 1);
           resolve({ chunk: base64Chunk });
@@ -93,12 +96,22 @@ export class ChunkUploader {
       }
     );
 
-    const chunkRightPos =
-      uploaded + this.chunkLen > file.size
-        ? file.size
-        : uploaded + this.chunkLen;
-    const blob = file.slice(uploaded, chunkRightPos);
-    this.reader.readAsDataURL(blob);
+    for (let i = 0; i < 3; i++) {
+      try {
+        const chunkRightPos =
+          uploaded + this.chunkLen > file.size
+            ? file.size
+            : uploaded + this.chunkLen;
+        const blob = file.slice(uploaded, chunkRightPos);
+        reader.readAsDataURL(blob);
+        break;
+      } catch (e) {
+        // The object is already busy reading Blobs
+        console.error(e);
+        await this.backOff();
+        continue;
+      }
+    }
 
     const result = await readerPromise;
     if (result.err != null) {
@@ -140,17 +153,17 @@ export class ChunkUploader {
       const uploadStatusResp = await this.client.uploadStatus(filePath);
       return uploadStatusResp.status === 200
         ? {
-            filePath,
-            uploaded: uploadStatusResp.data.uploaded,
-            state: UploadState.Ready,
-            err: "",
-          }
+          filePath,
+          uploaded: uploadStatusResp.data.uploaded,
+          state: UploadState.Ready,
+          err: "",
+        }
         : {
-            filePath,
-            uploaded: uploaded,
-            state: UploadState.Error,
-            err: `failed to get upload status: ${uploadStatusResp.statusText}`,
-          };
+          filePath,
+          uploaded: uploaded,
+          state: UploadState.Error,
+          err: `failed to get upload status: ${uploadStatusResp.statusText}`,
+        };
     } catch (e) {
       return {
         filePath,