ni18n ships with its own types and leverages the types from react-i18next.
Note: For a detailed instruction on creating your declaration file, read react-i18next docs
To allow a type safe integration you can create a new declaration file as seen in i18next.d.ts. Then make sure the file is loaded in your tsconfig.json under include.
With that done, your t, useTranslation, loadTranslations and clientNamespaces and other i18next functions will be properly typed and have autocomplete enabled.