How to Save your chat history on WhatsApp

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

To backup your chats, go to WhatsApp > Menu Button > Settings > Chats > Chat backup > Back Up.

To export a copy of the history of an individual chat or group, use the Email chat feature:
Open the chat for the individual or group. 

• Tap the Menu Button. 
• Tap More. 
• Tap Email chat. 
• Choose whether to Attach Media or not. 

An email will be composed with your chat history attached as a .txt document.

Note:
If you choose to attach media, the most recent media sent will be added as attachments.
When sending with media, you can send up to 10,000 latest messages. Without media, you can send 40,000 messages. These constraints are due to maximum email sizes.