WhatsApp is in the process of rolling out a two-step verification feature for the messaging platform from today. The security option has been in testing for several months, but is finally going live for all users of the app.
With the optional feature, WhatsApp users will be able to securely verify their number with a custom-generated six-digit passcode whenever they install the app on a new device. To activate the security feature, users should open the app and tap through to Settings -> Account -> Two-step verification -> Enable.
Upon enabling the feature, users are asked if they want to enter their email address. This is used by WhatsApp to send a link via email to disable two-step verification in case the six-digit passcode is forgotten, and also to help safeguard the account.
To help users remember their passcode, WhatsApp will periodically ask them for it. There is no option to disable this without disabling the two-step verification feature.
Source | macrumors