If you want to use WhatsApp without letting your contacts know that you are online, you can make your status appear as 'Offline.' This can be useful if you want to read messages without responding, or if you want to avoid being bothered by people while you are busy.
This will prevent your contacts from seeing when you were last online. However, it will also prevent you from seeing when they were last online.
There are a number of third-party apps that allow you to make your WhatsApp status appear as 'Offline.' One popular app is WhatsApp GB. This app has a number of features, including the ability to freeze your last seen, hide your online status, and schedule messages.
A VPN can be used to change your IP address and make it appear as though you are in a different location. This can be useful if you want to avoid being seen as online by people in your country.
It is important to note that these methods may not work for all users. WhatsApp is constantly updating its app, and it is possible that they will find a way to prevent these methods from working in the future.