diff --git a/app/controllers/concerns/switch_locale.rb b/app/controllers/concerns/switch_locale.rb
index 3013ff3cc..a8ea8ae05 100644
--- a/app/controllers/concerns/switch_locale.rb
+++ b/app/controllers/concerns/switch_locale.rb
@@ -5,10 +5,11 @@ module SwitchLocale
 
   def switch_locale(&)
     # priority is for locale set in query string (mostly for widget/from js sdk)
-    locale ||= locale_from_params
+    locale ||= params[:locale]
+
     locale ||= locale_from_custom_domain
     # if locale is not set in account, let's use DEFAULT_LOCALE env variable
-    locale ||= locale_from_env_variable
+    locale ||= ENV.fetch('DEFAULT_LOCALE', nil)
     set_locale(locale, &)
   end
 
@@ -32,26 +33,30 @@ module SwitchLocale
   end
 
   def set_locale(locale, &)
-    # if locale is empty, use default_locale
-    locale ||= I18n.default_locale
+    safe_locale = validate_and_get_locale(locale)
     # Ensure locale won't bleed into other requests
     # https://guides.rubyonrails.org/i18n.html#managing-the-locale-across-requests
-    I18n.with_locale(locale, &)
+    I18n.with_locale(safe_locale, &)
   end
 
-  def locale_from_params
-    I18n.available_locales.map(&:to_s).include?(params[:locale]) ? params[:locale] : nil
+  def validate_and_get_locale(locale)
+    return I18n.default_locale.to_s if locale.blank?
+
+    available_locales = I18n.available_locales.map(&:to_s)
+    locale_without_variant = locale.split('_')[0]
+
+    if available_locales.include?(locale)
+      locale
+    elsif available_locales.include?(locale_without_variant)
+      locale_without_variant
+    else
+      I18n.default_locale.to_s
+    end
   end
 
   def locale_from_account(account)
     return unless account
 
-    I18n.available_locales.map(&:to_s).include?(account.locale) ? account.locale : nil
-  end
-
-  def locale_from_env_variable
-    return unless ENV.fetch('DEFAULT_LOCALE', nil)
-
-    I18n.available_locales.map(&:to_s).include?(ENV.fetch('DEFAULT_LOCALE')) ? ENV.fetch('DEFAULT_LOCALE') : nil
+    account.locale
   end
 end
diff --git a/app/controllers/public/api/v1/portals/base_controller.rb b/app/controllers/public/api/v1/portals/base_controller.rb
index f6c10f7c4..66b052b1e 100644
--- a/app/controllers/public/api/v1/portals/base_controller.rb
+++ b/app/controllers/public/api/v1/portals/base_controller.rb
@@ -1,4 +1,6 @@
 class Public::Api::V1::Portals::BaseController < PublicController
+  include SwitchLocale
+
   before_action :show_plain_layout
   before_action :set_color_scheme
   before_action :set_global_config
@@ -27,14 +29,7 @@ class Public::Api::V1::Portals::BaseController < PublicController
   end
 
   def switch_locale_with_portal(&)
-    locale_without_variant = params[:locale].split('_')[0]
-    is_locale_available = I18n.available_locales.map(&:to_s).include?(params[:locale])
-    is_locale_variant_available = I18n.available_locales.map(&:to_s).include?(locale_without_variant)
-    if is_locale_available
-      @locale = params[:locale]
-    elsif is_locale_variant_available
-      @locale = locale_without_variant
-    end
+    @locale = validate_and_get_locale(params[:locale])
 
     I18n.with_locale(@locale, &)
   end
@@ -44,12 +39,12 @@ class Public::Api::V1::Portals::BaseController < PublicController
     Rails.logger.info "Article: not found for slug: #{params[:article_slug]}"
     render_404 && return if article.blank?
 
-    @locale = if article.category.present?
-                article.category.locale
-              else
-                article.portal.default_locale
-              end
-
+    article_locale = if article.category.present?
+                       article.category.locale
+                     else
+                       article.portal.default_locale
+                     end
+    @locale = validate_and_get_locale(article_locale)
     I18n.with_locale(@locale, &)
   end
 
diff --git a/spec/models/concerns/switch_locale_spec.rb b/spec/models/concerns/switch_locale_spec.rb
new file mode 100644
index 000000000..98628b92c
--- /dev/null
+++ b/spec/models/concerns/switch_locale_spec.rb
@@ -0,0 +1,74 @@
+require 'rails_helper'
+
+RSpec.describe 'SwitchLocale Concern', type: :controller do
+  controller(ApplicationController) do
+    include SwitchLocale
+
+    def index
+      switch_locale { render plain: I18n.locale }
+    end
+
+    def account_locale
+      switch_locale_using_account_locale { render plain: I18n.locale }
+    end
+  end
+
+  let(:account) { create(:account, locale: 'es') }
+  let(:portal) { create(:portal, custom_domain: 'custom.example.com', config: { default_locale: 'fr_FR' }) }
+
+  describe '#switch_locale' do
+    context 'when locale is provided in params' do
+      it 'sets locale from params' do
+        get :index, params: { locale: 'es' }
+        expect(response.body).to eq('es')
+      end
+
+      it 'falls back to default locale if invalid' do
+        get :index, params: { locale: 'invalid' }
+        expect(response.body).to eq('en')
+      end
+    end
+
+    context 'when request is from custom domain' do
+      before { request.host = portal.custom_domain }
+
+      it 'sets locale from portal' do
+        get :index
+        expect(response.body).to eq('fr')
+      end
+
+      it 'overrides portal locale with param' do
+        get :index, params: { locale: 'es' }
+        expect(response.body).to eq('es')
+      end
+    end
+
+    context 'when locale is not provided anywhere' do
+      it 'sets locale from environment variable' do
+        with_modified_env(DEFAULT_LOCALE: 'de_DE') do
+          get :index
+          expect(response.body).to eq('de')
+        end
+      end
+
+      it 'falls back to default locale if env locale invalid' do
+        with_modified_env(DEFAULT_LOCALE: 'invalid') do
+          get :index
+          expect(response.body).to eq('en')
+        end
+      end
+    end
+  end
+
+  describe '#switch_locale_using_account_locale' do
+    before do
+      routes.draw { get 'account_locale' => 'anonymous#account_locale' }
+    end
+
+    it 'sets locale from account' do
+      controller.instance_variable_set(:@current_account, account)
+      get :account_locale
+      expect(response.body).to eq('es')
+    end
+  end
+end