WHMCS includes multiple Client Area and store translations through files in the lang directory. You can choose whether to allow customers to select their own language from a language menu.
Enable the Language Menu
To enable the language menu in the Client Area:
1. Go to Configuration > System Settings > General Settings (Setup > General Settings prior to WHMCS 8.0).
2. Choose the Localization tab.
3. Check Enable Language Menu.

4. Click Save Changes.
Visitors will now see a button in the bottom-right corner of the page that they can use to select their preferred language.
