diff --git a/assets/translations/en.json b/assets/translations/en.json
index 45faa3e8..73c3575e 100644
--- a/assets/translations/en.json
+++ b/assets/translations/en.json
@@ -320,12 +320,13 @@
     "delete_ssh_key": "Delete SSH key for {}"
   },
   "validations": {
-    "required": "Required",
-    "invalid_format": "Invalid format",
-    "root_name": "User name cannot be 'root'",
-    "key_format": "Invalid key format",
-    "length": "Length is [] should be {}",
-    "user_already_exist": "Already exists",
-    "key_already_exists": "This key already exists"
+    "required": "Required.",
+    "invalid_format": "Invalid format.",
+    "root_name": "User name cannot be 'root'.",
+    "key_format": "Invalid key format.",
+    "length_not_equal": "Length is []. Should be {}.",
+    "length_longer": "Length is []. Should be shorter than or equal to {}.",
+    "user_already_exist": "This user already exists.",
+    "key_already_exists": "This key already exists."
   }
 }
diff --git a/assets/translations/ru.json b/assets/translations/ru.json
index 619096a7..ee085ed4 100644
--- a/assets/translations/ru.json
+++ b/assets/translations/ru.json
@@ -323,9 +323,10 @@
   "validations": {
     "required": "Обязательное поле.",
     "invalid_format": "Неверный формат.",
-    "root_name": "Имя пользователя не может быть'root'.",
+    "root_name": "Имя пользователя не может быть 'root'.",
     "key_format": "Неверный формат.",
-    "length": "Длина строки [] должна быть {}.",
+    "length_not_equal": "Длина строки []. Должно быть равно {}.",
+    "length_longer": "Длина строки []. Должно быть меньше либо равно {}.",
     "user_already_exist": "Имя уже используется.",
     "key_already_exists": "Этот ключ уже добавлен."
   }
diff --git a/lib/logic/api_maps/server.dart b/lib/logic/api_maps/server.dart
index 0e8930e5..6302611e 100644
--- a/lib/logic/api_maps/server.dart
+++ b/lib/logic/api_maps/server.dart
@@ -18,7 +18,7 @@ class ApiResponse<D> {
   final String? errorMessage;
   final D data;
 
-  get isSuccess => statusCode >= 200 && statusCode < 300;
+  bool get isSuccess => statusCode >= 200 && statusCode < 300;
 
   ApiResponse({
     required this.statusCode,
@@ -65,27 +65,47 @@ class ServerApi extends ApiMap {
   }
 
   Future<ApiResponse<User>> createUser(User user) async {
-    Response response;
-
     var client = await getClient();
-    // POST request with JSON body containing username and password
 
-    response = await client.post(
-      '/users',
-      data: {
-        'username': user.login,
-        'password': user.password,
-      },
-      options: Options(
-        contentType: 'application/json',
-      ),
-    );
-
-    close(client);
-
-    if (response.statusCode == HttpStatus.created) {
+    var makeErrorApiReponse = (int status) {
       return ApiResponse(
-        statusCode: response.statusCode ?? HttpStatus.internalServerError,
+        statusCode: status,
+        data: User(
+          login: user.login,
+          password: user.password,
+          isFoundOnServer: false,
+        ),
+      );
+    };
+
+    late Response<dynamic> response;
+
+    try {
+      response = await client.post(
+        '/users',
+        data: {
+          'username': user.login,
+          'password': user.password,
+        },
+        options: Options(
+            contentType: 'application/json',
+            receiveDataWhenStatusError: true,
+            followRedirects: false,
+            validateStatus: (status) {
+              return (status != null) &&
+                  (status < HttpStatus.internalServerError);
+            }),
+      );
+    } catch (e) {
+      return makeErrorApiReponse(HttpStatus.internalServerError);
+    } finally {
+      close(client);
+    }
+
+    if ((response.statusCode != null) &&
+        (response.statusCode == HttpStatus.created)) {
+      return ApiResponse(
+        statusCode: response.statusCode!,
         data: User(
           login: user.login,
           password: user.password,
@@ -93,18 +113,11 @@ class ServerApi extends ApiMap {
         ),
       );
     } else {
-      return ApiResponse(
-        statusCode: response.statusCode ?? HttpStatus.internalServerError,
-        data: User(
-          login: user.login,
-          password: user.password,
-          isFoundOnServer: false,
-          note: response.data['message'] ?? null,
-        ),
-        errorMessage: response.data?.containsKey('error') ?? false
-            ? response.data['error']
-            : null,
-      );
+      print(response.statusCode.toString() +
+          ": " +
+          (response.statusMessage ?? ""));
+      return makeErrorApiReponse(
+          response.statusCode ?? HttpStatus.internalServerError);
     }
   }
 
diff --git a/lib/logic/cubit/forms/factories/field_cubit_factory.dart b/lib/logic/cubit/forms/factories/field_cubit_factory.dart
new file mode 100644
index 00000000..d3255a5f
--- /dev/null
+++ b/lib/logic/cubit/forms/factories/field_cubit_factory.dart
@@ -0,0 +1,56 @@
+import 'package:flutter/material.dart';
+import 'package:selfprivacy/logic/cubit/forms/validations/validations.dart';
+import 'package:easy_localization/easy_localization.dart';
+import 'package:cubit_form/cubit_form.dart';
+import 'package:selfprivacy/logic/cubit/users/users_cubit.dart';
+
+class FieldCubitFactory {
+  FieldCubitFactory(this.context);
+
+  /// A common user login field.
+  ///
+  /// - Available characters are lowercase a-z, digits and underscore _
+  /// - Must start with either a-z or underscore
+  /// - Must be no longer than 'userMaxLength' characters
+  /// - Must not be empty
+  /// - Must not be a reserved root login
+  /// - Must be unique
+  FieldCubit<String> createUserLoginField() {
+    final userAllowedRegExp = RegExp(r"^[a-z_][a-z0-9_]+$");
+    const userMaxLength = 31;
+    return FieldCubit(
+      initalValue: '',
+      validations: [
+        ValidationModel<String>(
+            (s) => s.toLowerCase() == 'root', 'validations.root_name'.tr()),
+        ValidationModel(
+          (login) => context.read<UsersCubit>().state.isLoginRegistered(login),
+          'validations.user_already_exist'.tr(),
+        ),
+        RequiredStringValidation('validations.required'.tr()),
+        LengthStringLongerValidation(userMaxLength),
+        ValidationModel<String>((s) => !userAllowedRegExp.hasMatch(s),
+            'validations.invalid_format'.tr()),
+      ],
+    );
+  }
+
+  /// A common user password field.
+  ///
+  /// - Must fail on the regural expression of invalid matches: [\n\r\s]+
+  /// - Must not be empty
+  FieldCubit<String> createUserPasswordField() {
+    var passwordForbiddenRegExp = RegExp(r"[\n\r\s]+");
+    return FieldCubit(
+      initalValue: '',
+      validations: [
+        RequiredStringValidation('validations.required'.tr()),
+        ValidationModel<String>(
+            (password) => passwordForbiddenRegExp.hasMatch(password),
+            'validations.invalid_format'.tr()),
+      ],
+    );
+  }
+
+  final BuildContext context;
+}
diff --git a/lib/logic/cubit/forms/initializing/backblaze_form_cubit.dart b/lib/logic/cubit/forms/initializing/backblaze_form_cubit.dart
index eda06939..d8777fa8 100644
--- a/lib/logic/cubit/forms/initializing/backblaze_form_cubit.dart
+++ b/lib/logic/cubit/forms/initializing/backblaze_form_cubit.dart
@@ -12,9 +12,6 @@ class BackblazeFormCubit extends FormCubit {
       initalValue: '',
       validations: [
         RequiredStringValidation('validations.required'.tr()),
-        //ValidationModel<String>(
-        //(s) => regExp.hasMatch(s), 'invalid key format'),
-        //LegnthStringValidationWithLenghShowing(64, 'length is [] shoud be 64')
       ],
     );
 
@@ -22,9 +19,6 @@ class BackblazeFormCubit extends FormCubit {
       initalValue: '',
       validations: [
         RequiredStringValidation('required'),
-        //ValidationModel<String>(
-        //(s) => regExp.hasMatch(s), 'invalid key format'),
-        //LegnthStringValidationWithLenghShowing(64, 'length is [] shoud be 64')
       ],
     );
 
diff --git a/lib/logic/cubit/forms/initializing/cloudflare_form_cubit.dart b/lib/logic/cubit/forms/initializing/cloudflare_form_cubit.dart
index 7ee8c8fa..d811843b 100644
--- a/lib/logic/cubit/forms/initializing/cloudflare_form_cubit.dart
+++ b/lib/logic/cubit/forms/initializing/cloudflare_form_cubit.dart
@@ -4,8 +4,7 @@ import 'package:cubit_form/cubit_form.dart';
 import 'package:easy_localization/easy_localization.dart';
 import 'package:selfprivacy/logic/api_maps/cloudflare.dart';
 import 'package:selfprivacy/logic/cubit/app_config/app_config_cubit.dart';
-
-import '../validations/validations.dart';
+import 'package:selfprivacy/logic/cubit/forms/validations/validations.dart';
 
 class CloudFlareFormCubit extends FormCubit {
   CloudFlareFormCubit(this.initializingCubit) {
@@ -16,12 +15,7 @@ class CloudFlareFormCubit extends FormCubit {
         RequiredStringValidation('validations.required'.tr()),
         ValidationModel<String>(
             (s) => regExp.hasMatch(s), 'validations.key_format'.tr()),
-        LengthStringValidationWithLengthShowing(
-          40,
-          'validations.length'.tr(
-            args: ["40"],
-          ),
-        )
+        LengthStringNotEqualValidation(40)
       ],
     );
 
diff --git a/lib/logic/cubit/forms/initializing/hetzner_form_cubit.dart b/lib/logic/cubit/forms/initializing/hetzner_form_cubit.dart
index 55af50d9..ce3e5aa9 100644
--- a/lib/logic/cubit/forms/initializing/hetzner_form_cubit.dart
+++ b/lib/logic/cubit/forms/initializing/hetzner_form_cubit.dart
@@ -4,8 +4,7 @@ import 'package:cubit_form/cubit_form.dart';
 import 'package:easy_localization/easy_localization.dart';
 import 'package:selfprivacy/logic/api_maps/hetzner.dart';
 import 'package:selfprivacy/logic/cubit/app_config/app_config_cubit.dart';
-
-import '../validations/validations.dart';
+import 'package:selfprivacy/logic/cubit/forms/validations/validations.dart';
 
 class HetznerFormCubit extends FormCubit {
   HetznerFormCubit(this.initializingCubit) {
@@ -16,8 +15,7 @@ class HetznerFormCubit extends FormCubit {
         RequiredStringValidation('validations.required'.tr()),
         ValidationModel<String>(
             (s) => regExp.hasMatch(s), 'validations.key_format'.tr()),
-        LengthStringValidationWithLengthShowing(
-            64, 'validations.length'.tr(args: ["64"]))
+        LengthStringNotEqualValidation(64)
       ],
     );
 
diff --git a/lib/logic/cubit/forms/initializing/root_user_form_cubit.dart b/lib/logic/cubit/forms/initializing/root_user_form_cubit.dart
index 41b26582..102d7ac7 100644
--- a/lib/logic/cubit/forms/initializing/root_user_form_cubit.dart
+++ b/lib/logic/cubit/forms/initializing/root_user_form_cubit.dart
@@ -2,33 +2,14 @@ import 'dart:async';
 
 import 'package:cubit_form/cubit_form.dart';
 import 'package:selfprivacy/logic/cubit/app_config/app_config_cubit.dart';
+import 'package:selfprivacy/logic/cubit/forms/factories/field_cubit_factory.dart';
 import 'package:selfprivacy/logic/models/user.dart';
-import 'package:easy_localization/easy_localization.dart';
 
 class RootUserFormCubit extends FormCubit {
-  RootUserFormCubit(this.initializingCubit) {
-    var userRegExp = RegExp(r"\W");
-    var passwordRegExp = RegExp(r"[\n\r\s]+");
-
-    userName = FieldCubit(
-      initalValue: '',
-      validations: [
-        ValidationModel<String>(
-            (s) => s.toLowerCase() == 'root', 'validations.root_name'.tr()),
-        RequiredStringValidation('validations.required'.tr()),
-        ValidationModel<String>(
-            (s) => userRegExp.hasMatch(s), 'validations.invalid_format'.tr()),
-      ],
-    );
-
-    password = FieldCubit(
-      initalValue: '',
-      validations: [
-        RequiredStringValidation('validations.required'.tr()),
-        ValidationModel<String>((s) => passwordRegExp.hasMatch(s),
-            'validations.invalid_format'.tr()),
-      ],
-    );
+  RootUserFormCubit(
+      this.initializingCubit, final FieldCubitFactory fieldFactory) {
+    userName = fieldFactory.createUserLoginField();
+    password = fieldFactory.createUserPasswordField();
 
     isVisible = FieldCubit(initalValue: false);
 
diff --git a/lib/logic/cubit/forms/user/user_form_cubit.dart b/lib/logic/cubit/forms/user/user_form_cubit.dart
index 24f67437..b65cfb47 100644
--- a/lib/logic/cubit/forms/user/user_form_cubit.dart
+++ b/lib/logic/cubit/forms/user/user_form_cubit.dart
@@ -1,7 +1,7 @@
 import 'dart:async';
 
 import 'package:cubit_form/cubit_form.dart';
-import 'package:easy_localization/easy_localization.dart';
+import 'package:selfprivacy/logic/cubit/forms/factories/field_cubit_factory.dart';
 import 'package:selfprivacy/logic/cubit/jobs/jobs_cubit.dart';
 import 'package:selfprivacy/logic/models/job.dart';
 import 'package:selfprivacy/logic/models/user.dart';
@@ -10,38 +10,16 @@ import 'package:selfprivacy/utils/password_generator.dart';
 class UserFormCubit extends FormCubit {
   UserFormCubit({
     required this.jobsCubit,
-    required List<User> users,
+    required FieldCubitFactory fieldFactory,
     User? user,
   }) {
     var isEdit = user != null;
 
-    var userRegExp = RegExp(r"\W");
-    var passwordRegExp = RegExp(r"[\n\r\s]+");
-
-    login = FieldCubit(
-      initalValue: isEdit ? user!.login : '',
-      validations: [
-        ValidationModel<String>(
-            (s) => s.toLowerCase() == 'root', 'validations.root_name'.tr()),
-        ValidationModel(
-          (login) => users.any((user) => user.login == login),
-          'validations.user_already_exist'.tr(),
-        ),
-        RequiredStringValidation('validations.required'.tr()),
-        ValidationModel<String>(
-            (s) => userRegExp.hasMatch(s), 'validations.invalid_format'.tr()),
-      ],
-    );
-
-    password = FieldCubit(
-      initalValue:
-          isEdit ? (user?.password ?? '') : StringGenerators.userPassword(),
-      validations: [
-        RequiredStringValidation('validations.required'.tr()),
-        ValidationModel<String>((s) => passwordRegExp.hasMatch(s),
-            'validations.invalid_format'.tr()),
-      ],
-    );
+    login = fieldFactory.createUserLoginField();
+    login.setValue(isEdit ? user!.login : '');
+    password = fieldFactory.createUserPasswordField();
+    password.setValue(
+        isEdit ? (user?.password ?? '') : StringGenerators.userPassword());
 
     super.addFields([login, password]);
   }
diff --git a/lib/logic/cubit/forms/validations/validations.dart b/lib/logic/cubit/forms/validations/validations.dart
index aff4ec92..91a8f75c 100644
--- a/lib/logic/cubit/forms/validations/validations.dart
+++ b/lib/logic/cubit/forms/validations/validations.dart
@@ -1,13 +1,28 @@
 import 'package:cubit_form/cubit_form.dart';
+import 'package:easy_localization/easy_localization.dart';
 
-class LengthStringValidationWithLengthShowing extends ValidationModel<String> {
-  LengthStringValidationWithLengthShowing(int length, String errorText)
-      : super((n) => n.length != length, errorText);
+abstract class LengthStringValidation extends ValidationModel<String> {
+  LengthStringValidation(bool Function(String) predicate, String errorMessage)
+      : super(predicate, errorMessage);
 
   @override
-  String? check(String val) {
-    var length = val.length;
-    var errorMassage = this.errorMassage.replaceAll("[]", length.toString());
-    return test(val) ? errorMassage : null;
+  String? check(String value) {
+    var length = value.length;
+    var errorMessage = this.errorMassage.replaceAll("[]", length.toString());
+    return test(value) ? errorMessage : null;
   }
 }
+
+class LengthStringNotEqualValidation extends LengthStringValidation {
+  /// String must be equal to [length]
+  LengthStringNotEqualValidation(int length)
+      : super((n) => n.length != length,
+            'validations.length_not_equal'.tr(args: [length.toString()]));
+}
+
+class LengthStringLongerValidation extends LengthStringValidation {
+  /// String must be shorter than or equal to [length]
+  LengthStringLongerValidation(int length)
+      : super((n) => n.length > length,
+            'validations.length_longer'.tr(args: [length.toString()]));
+}
diff --git a/lib/logic/cubit/users/users_cubit.dart b/lib/logic/cubit/users/users_cubit.dart
index 65967a9a..0fd27064 100644
--- a/lib/logic/cubit/users/users_cubit.dart
+++ b/lib/logic/cubit/users/users_cubit.dart
@@ -160,7 +160,12 @@ class UsersCubit extends AppConfigDependendCubit<UsersState> {
     if (user.login == 'root' || user.login == state.primaryUser.login) {
       return;
     }
+    // If API returned error, do nothing
     final result = await api.createUser(user);
+    if (!result.isSuccess) {
+      return;
+    }
+
     var loadedUsers = List<User>.from(state.users);
     loadedUsers.add(result.data);
     await box.clear();
diff --git a/lib/logic/cubit/users/users_state.dart b/lib/logic/cubit/users/users_state.dart
index 1ee1903f..d15789c9 100644
--- a/lib/logic/cubit/users/users_state.dart
+++ b/lib/logic/cubit/users/users_state.dart
@@ -22,5 +22,11 @@ class UsersState extends AppConfigDependendState {
     );
   }
 
+  bool isLoginRegistered(String login) {
+    return users.any((user) => user.login == login) ||
+        login == rootUser.login ||
+        login == primaryUser.login;
+  }
+
   bool get isEmpty => users.isEmpty;
 }
diff --git a/lib/main.dart b/lib/main.dart
index db3f3b96..e5af3656 100644
--- a/lib/main.dart
+++ b/lib/main.dart
@@ -22,8 +22,8 @@ void main() async {
   await SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
 
   try {
-    /* Wakelock support for Linux
-     * desktop is not yet implemented */
+    /// Wakelock support for Linux
+    /// desktop is not yet implemented
     await Wakelock.enable();
   } on PlatformException catch (e) {
     print(e);
diff --git a/lib/ui/pages/initializing/initializing.dart b/lib/ui/pages/initializing/initializing.dart
index 95ba575c..d30569ca 100644
--- a/lib/ui/pages/initializing/initializing.dart
+++ b/lib/ui/pages/initializing/initializing.dart
@@ -3,6 +3,7 @@ import 'package:easy_localization/easy_localization.dart';
 import 'package:flutter/material.dart';
 import 'package:selfprivacy/config/brand_theme.dart';
 import 'package:selfprivacy/logic/cubit/app_config/app_config_cubit.dart';
+import 'package:selfprivacy/logic/cubit/forms/factories/field_cubit_factory.dart';
 import 'package:selfprivacy/logic/cubit/forms/initializing/backblaze_form_cubit.dart';
 import 'package:selfprivacy/logic/cubit/forms/initializing/cloudflare_form_cubit.dart';
 import 'package:selfprivacy/logic/cubit/forms/initializing/domain_cloudflare.dart';
@@ -352,7 +353,8 @@ class InitializingPage extends StatelessWidget {
 
   Widget _stepUser(AppConfigCubit initializingCubit) {
     return BlocProvider(
-      create: (context) => RootUserFormCubit(initializingCubit),
+      create: (context) =>
+          RootUserFormCubit(initializingCubit, FieldCubitFactory(context)),
       child: Builder(builder: (context) {
         var formCubitState = context.watch<RootUserFormCubit>().state;
 
diff --git a/lib/ui/pages/users/new_user.dart b/lib/ui/pages/users/new_user.dart
index 4f6da178..58559c8f 100644
--- a/lib/ui/pages/users/new_user.dart
+++ b/lib/ui/pages/users/new_user.dart
@@ -24,7 +24,7 @@ class _NewUser extends StatelessWidget {
           }
           return UserFormCubit(
             jobsCubit: jobCubit,
-            users: users,
+            fieldFactory: FieldCubitFactory(context),
           );
         },
         child: Builder(builder: (context) {
diff --git a/lib/ui/pages/users/users.dart b/lib/ui/pages/users/users.dart
index 72c519a0..013f65b0 100644
--- a/lib/ui/pages/users/users.dart
+++ b/lib/ui/pages/users/users.dart
@@ -6,6 +6,7 @@ import 'package:selfprivacy/config/brand_colors.dart';
 import 'package:selfprivacy/config/brand_theme.dart';
 import 'package:selfprivacy/config/text_themes.dart';
 import 'package:selfprivacy/logic/cubit/app_config/app_config_cubit.dart';
+import 'package:selfprivacy/logic/cubit/forms/factories/field_cubit_factory.dart';
 import 'package:selfprivacy/logic/cubit/forms/user/user_form_cubit.dart';
 import 'package:selfprivacy/logic/cubit/jobs/jobs_cubit.dart';
 import 'package:selfprivacy/logic/cubit/users/users_cubit.dart';