Some mobiles allow you to use two WhatsApp accounts on the same phone, but what if you want to do the opposite? Namely, use the same WhatsApp account on two different phones. It’s also possible, even though the app doesn’t officially support it.
While we wait for WhatsApp’s new multi-device mode to allow us to use the same account on multiple phones and tablets, the second best way to do it is via WhatsApp Web. It has its drawbacks, but it is very easy and you avoid using third-party applications, with the security problems that they can cause.
Your WhatsApp on two mobiles
Today you can use WhatsApp only on one mobile at a time, for better or worse. The only exception is using WhatsApp for PC or WhatsApp Web, but neither of these tools are developed with mobile in mind.
WhatsApp’s new multi-device mode -which does not require the mobile to be turned on and connected- made us think that perhaps in the future the app will enable us to use our account on more than one mobile, but for now this has not happened. What you can do is use WhatsApp Web on your second mobile. To do this, on the mobile where you have WhatsApp installed, you must follow the same process as always to link a new device: open the Linked devices menu and press Link a device.

The next part of the process must be carried out on your second mobile, the one that does not have the WhatsApp account configured in it. Open the browser and enter https://web.whatsapp.com, the WhatsApp Web address.
WhatsApp Web does not have a mobile version at the moment, so it will not appear at first. To do so, you will need to open the browser menu and select computer view. You will then be able to see the QR code that you must scan using the mobile on which you have WhatsApp.

Scan the code with WhatsApp on your mobile and the session will start, effectively having WhatsApp on two mobiles. With the new multi-device mode, in addition you can use whatsapp on this second mobile when the other is offwhich is a nice addition.
To have faster access to WhatsApp on this second mobile you can add a shortcut to your mobile, to open it with a touch. To do this, open the menu and go to Add to home screen.

WhatsApp Web is not designed to be used on small mobile screens, so it can be a bit frustrating to use on mobile, although you will not have any problems using it on a tablet.
On a mobile, it is recommended that you use it with the screen horizontal, so you can see the entire interface without having to scroll in all directions. Even better if you use the mobile paired with a physical keyboard, so that the virtual keyboard does not overlap the interface.

WhatsApp Web is not adapted for mobiles, so it is better to use it horizontally
Using WhatsApp Web to have WhatsApp on a second mobile is a very interesting trick for emergencies, although it does not give the same experience as using WhatsApp in its application. Hopefully, in the future, WhatsApp will allow us to use your account in various mobile apps. officially, although at the moment it has not been confirmed that this will exist.