Your WhatsApp messages are automatically backed up and saved daily to your phone's memory. Depending on your settings, you can also periodically back up your WhatsApp chats to OneDrive. If you uninstall WhatsApp from your phone, but don't want to lose any of your messages, be sure to manually back up or export your chats before uninstalling.

To back up your chats

1. Open WhatsApp and tap on More > settings > chats and calls.
2. Tap backup.

If you want to restore the backup, please read this article.

To export your chats

If you would like to keep a record of your messages on a computer or in an email, you can email yourself individual chats. Please follow these steps:

1. Open the chat you wish to export.
2. Tap on More > info or group info.
3. Tap on More > email chat history.

Notes:
* It is not possible to attach chat media in the email at this time.
* Your chat history will be attached to the generated email as a .txt file (Windows Phone 8.1 and later) or pasted into the body of the email (Windows Phone 7 and 8.0).
* You may not be able to email your entire chat history due to Windows Mail size restrictions. The only way to export newer messages would be to delete older messages and then email your chat history again.

Learn how to save chat history on: Android | iPhone