diff --git a/NEWS b/NEWS
index d08a558e6..f7df48a24 100644
--- a/NEWS
+++ b/NEWS
@@ -8,6 +8,7 @@ Enhancements
  - [web] add rel="noopener" to external links (#4764)
  - [web] add Indonesian (id) translation
  - [web] updated Angular Material to version 1.1.19
+ - [web] replaced bower packages by npm packages
 
 Bug fixes
  - [web] fixed wrong translation of custom calendar categories
diff --git a/UI/WebServerResources/GNUmakefile b/UI/WebServerResources/GNUmakefile
index af3389e2f..84c686f94 100644
--- a/UI/WebServerResources/GNUmakefile
+++ b/UI/WebServerResources/GNUmakefile
@@ -10,16 +10,11 @@ CSS_FILES = css/styles.css css/styles.css.map css/no-animation.css  css/no-anima
 .DEFAULT_GOAL := all
 
 dev:
-	npm install --production
+	npm install
 	@if [ ! -e angular-material/src ]; then \
 	  git submodule init; \
 	fi
 	git submodule update
-	@if [ -d bower_components ]; then \
-	  bower update --allow-root; \
-	else \
-	  bower install --allow-root; \
-	fi
 	grunt --stack build
 
 prod:
diff --git a/UI/WebServerResources/Gruntfile.js b/UI/WebServerResources/Gruntfile.js
index 0c6a46bab..037ebdbfa 100644
--- a/UI/WebServerResources/Gruntfile.js
+++ b/UI/WebServerResources/Gruntfile.js
@@ -17,8 +17,8 @@ module.exports = function(grunt) {
 
   };
   var custom_vendor_files = {
-    'js/vendor/angular-file-upload.min.js': ['bower_components/angular-file-upload/dist/angular-file-upload.js', 'js/Common/angular-file-upload.trump.js'],
-    'js/vendor/FileSaver.min.js': ['bower_components/FileSaver/dist/FileSaver.js']
+    'js/vendor/angular-file-upload.min.js': ['node_modules/angular-file-upload/dist/angular-file-upload.js', 'js/Common/angular-file-upload.trump.js'],
+    'js/vendor/FileSaver.min.js': ['node_modules/file-saver/dist/FileSaver.js']
   };
 
   require('time-grunt')(grunt);
@@ -32,7 +32,7 @@ module.exports = function(grunt) {
         outFile: 'css/styles.css',
         noCache: true,
         includePaths: ['scss/',
-                       'bower_components/breakpoint-sass/stylesheets/'
+                       'node_modules/breakpoint-sass/stylesheets/'
         ]
       },
       target: {
@@ -48,15 +48,8 @@ module.exports = function(grunt) {
           map: true,
           processors: [
             // See angular-material/gulp/util.js
-            require('autoprefixer')({
-              browsers: [
-                'last 2 versions',
-                'not ie <= 10',
-                'not ie_mob <= 10',
-                'last 4 Android versions',
-                'Safari >= 8'
-              ]
-            })
+            // See browserslist in package.json
+            require('autoprefixer')()
           ]
         },
         src: ['css/styles.css', 'css/no-animation.css']
@@ -127,7 +120,7 @@ module.exports = function(grunt) {
   // Register Grunt tasks
   grunt.task.registerTask('static', function() {
     var options = {
-      'src': 'bower_components',
+      'src': 'node_modules',
       'js_dest': 'js/vendor/',
       'fonts_dest': 'fonts/',
       'css_dest': 'css/'
diff --git a/UI/WebServerResources/bower.json b/UI/WebServerResources/bower.json
deleted file mode 100644
index 38a77557c..000000000
--- a/UI/WebServerResources/bower.json
+++ /dev/null
@@ -1,19 +0,0 @@
-{
-  "name": "sogo-web",
-  "private": true,
-  "devDependencies": {
-    "angular": "1.7.x",
-    "angular-animate": "1.7.x",
-    "angular-aria": "1.7.x",
-    "angular-cookies": "1.7.x",
-    "angular-messages": "1.7.x",
-    "angular-sanitize": "1.7.x",
-    "angular-ui-router": "1.0.20",
-    "angular-file-upload": "latest",
-    "angular-material": "1.1.19",
-    "FileSaver": "latest",
-    "lodash": "latest",
-    "ng-sortable": "1.3.7",
-    "breakpoint-sass": ">=2.4.2"
-  }
-}
diff --git a/UI/WebServerResources/js/Scheduler/Attendees.service.js b/UI/WebServerResources/js/Scheduler/Attendees.service.js
index 67d050413..ab47799c5 100644
--- a/UI/WebServerResources/js/Scheduler/Attendees.service.js
+++ b/UI/WebServerResources/js/Scheduler/Attendees.service.js
@@ -631,7 +631,7 @@
       _this.currentEntries = _.flatMap(_this.component.organizer.freebusy[startDay]);
       for (i = 0; i < _this.component.attendees.length; i++) {
         attendee = _this.component.attendees[i];
-        if (attendee.role !== Attendees.ROLES.NON_PARTICIPANT) {
+        if (attendee.freebusy && attendee.role !== Attendees.ROLES.NON_PARTICIPANT) {
           attendeeEntries = _.flatMap(attendee.freebusy[startDay]);
           for (j = 0; j < _this.currentEntries.length; j++) {
             _this.currentEntries[j] += attendeeEntries[j];
diff --git a/UI/WebServerResources/package.json b/UI/WebServerResources/package.json
index 6ccd6bc4c..293100d12 100644
--- a/UI/WebServerResources/package.json
+++ b/UI/WebServerResources/package.json
@@ -1,21 +1,41 @@
 {
   "name": "sogo-web",
-  "version": "3.0.0",
-  "homepage": "http://sogo.nu",
-  "bugs": "http://sogo.nu/bugs",
+  "homepage": "https://sogo.nu",
+  "bugs": "https://sogo.nu/bugs",
+  "dependencies": {
+    "angular": "1.7.x",
+    "angular-animate": "1.7.x",
+    "angular-aria": "1.7.x",
+    "angular-cookies": "1.7.x",
+    "angular-file-upload": "latest",
+    "angular-material": "1.1.19",
+    "angular-messages": "1.7.x",
+    "angular-sanitize": "1.7.x",
+    "angular-ui-router": "1.0.20",
+    "file-saver": "latest",
+    "lodash": "latest",
+    "ng-sortable": "1.3.7"
+  },
   "devDependencies": {
     "autoprefixer": ">=6.0.3",
-    "bower": ">=1.3.8",
+    "breakpoint-sass": ">=2.4.2",
     "csswring": ">=3.0.0",
     "grunt": ">=0.4.1",
+    "grunt-contrib-cssmin": ">=1.0.0",
     "grunt-contrib-jshint": ">=0.11.2",
     "grunt-contrib-uglify": ">=0.9",
     "grunt-contrib-watch": ">=0.5.3",
-    "grunt-contrib-cssmin": ">=1.0.0",
     "grunt-ng-annotate": ">=0.10.0",
     "grunt-postcss": ">=0.6.0",
     "grunt-sass": "^2.0.0",
-    "time-grunt": "latest",
-    "kss": ">=2.1.0"
-  }
+    "kss": ">=2.1.0",
+    "time-grunt": "latest"
+  },
+  "browserslist": [
+    "last 2 versions",
+    "not ie <= 10",
+    "not ie_mob <= 10",
+    "last 4 Android versions",
+    "Safari >= 8"
+  ]
 }