If I install WhatsApp on another phone, will the messages be saved on the old phone - briefly?
If you install WhatsApp on another phone, your messages will not be automatically saved on the old phone. To ensure you have access to your message history, make sure to back up your chats before switching devices.
If I install WhatsApp on another phone, will the messages be saved on the old phone - in detail?
If you decide to install WhatsApp on a new device, the fate of your messages on the old phone largely depends on whether or not you choose to back up and restore your chat history.
By default, when you set up WhatsApp on a new device and verify your phone number, the app will prompt you to restore your chat history from a backup if one is available. This backup is typically stored in your cloud storage (iCloud for iOS users and Google Drive for Android users), not on the old phone itself. If you have enabled automatic backups, WhatsApp will regularly save your messages, media, and other data to the cloud.
If you opt to restore this backup on your new device, your chat history, including messages, photos, and videos, will be transferred to the new phone. However, this action does not delete the data from the old phone immediately; it remains until you manually delete the WhatsApp app or the backup file from your cloud storage.
On the other hand, if you do not restore a backup on the new device or choose to start fresh without transferring any data, your messages will remain on the old phone. They will continue to be accessible as long as WhatsApp is installed and not deleted from the old device. Keep in mind that once you delete the app or uninstall it from the old phone, all locally stored chat history will also be removed unless you have a recent backup saved in your cloud storage.
In summary, whether your messages are saved on the old phone after installing WhatsApp on another device depends on your actions during the setup process and the presence of a recent backup. To ensure your data is preserved, it's recommended to always enable automatic backups and verify that your chat history is safely stored in your cloud account.