To activate an account on WhatsApp, you know, you need to verify your identity using a valid mobile number: this is why the app has never officially landed on tablets (and probably never will). But if I used the term "official" it is because there are tricks that allow you to install WhatsApp on tablet bypassing, at least partially, the obstacle.
I warn you, these are not very comfortable procedures to put into practice, moreover the final result is not always 100% guaranteed, but for the moment they represent the only viable ways to have WhatsApp on Android tablets and iPads (including models equipped with Wi-Fi connection only). The secret - if we want to call it that - consists in forcing the installation of the app on your device and activating a new account using a mobile number not yet registered on WhatsApp (that of a traditional mobile phone is fine too, it doesn't have to be a smartphone). If you use a number already registered on the service, you will lose the ability to access WhatsApp with your phone as WhatsApp limits access to only one device per number).
Alternatively, if you want to use the same WhatsApp account on your smartphone and tablet, you can download applications that allow you to use WhatsApp Web on your tablet. In this way the tablet acts as a "repeater" of the smartphone (which must remain on and connected to the Internet) and allows you to chat on WhatsApp without losing access to the latter. Read on if you want to know more.
App to use WhatsApp Web on the tablet
As just mentioned, the easiest way to install WhatsApp on tablet is to resort to apps that allow you to use WhatsApp Web on these devices. By taking advantage of WhatsApp Web you can use your tablet as a "repeater" of the WhatsApp you have installed on your phone and access the service always using the same account. The only limitation of this procedure is that the smartphone on which the official version of WhatsApp is installed must always be switched on and connected to the Internet (even in 3G / LTE, even if Wi-Fi is recommended so as not to consume too much data traffic) .
By opening the Android and iPad stores you can find dozens of apps that allow you to take advantage of WhatsApp from your tablet, among the most interesting of the moment I point out Tablet for WhatsApp for Android and WhatsPad Messenger for iPad which are both free and work very simply.
To use the apps in question, all you have to do is start them and frame the QR Code that appears on the tablet screen using the smartphone (and therefore the appropriate WhatsApp function). If you don't know how to scan the WhatsApp Web QR Code with your smartphone, start WhatsApp, press the button (...) (or select the tab Settings if you are using an iPhone), "tap" on the icon related to Web WhatsApp e pulsing sul pulsating Ok ho capito.
Mission accomplished! You have successfully scanned the QR code and then you can start using WhatsApp on your tablet. Leaving the check mark next to the item Stay connected you can make the application "remember" your identity and therefore no longer ask you to frame the QR code.
Please note: if you want, you can also access WhatsApp Web using the browser included "as standard" on your tablet (eg Chrome on Android or Safari on iPad), by visiting the address web.whatsapp.com and activating the desktop view of the latter, but it is an unnecessarily more complicated operation than installing apps like the ones I just pointed out to you.
WhatsApp for Android tablets
If you search for WhatsApp on the Play Store using your Android tablet, you will hardly find it: that's why you have to get the apk package of the application and install it "manually".
No, don't worry, it's not about anything complex. All you have to do is open the browser (eg. Chrome), connect to whatsapp.com/android and press the button Download Now. Then go to the settings Android, select the item Safety and activate the option relative to Unknown origin to allow manual installation of apps.
When the operation is complete, expand the Android notification menu, select the icon WhatsApp.apk and proceed with the installation of the app by pressing first on NEXT and then Install e end. If you can't find the WhatsApp icon in the Android notification menu, open the app Download and select it from the latter; or download the free file manager ES File Manager and use its feature Install to complete the WhatsApp installation.
Now you have to go through the initial WhatsApp setup procedure normally (or almost). Then start the app and press the button Continue. If warnings appear relating to the fact that WhatsApp is not compatible with tablets or Android custom ROMs, ignore them by pressing on OK.
At this point, type in the number of the mobile phone you want to use to activate the service (complete with international prefix) and press on OK twice in a row. A 5-minute countdown will start during which the service will attempt to automatically activate your account, which will fail because the tablet you are using is not physically connected to the phone number you indicated for registration.
What you have to do is wait for the countdown to finish and type the verification code you received via SMS on your mobile phone to manually activate your account. If you have not received the message, press the button Call me and enter the code that will be dictated by phone (always on the mobile number you indicated above).
Mission accomplished! You have just completed the steps for install WhatsApp on tablet. Then choose the username and profile picture to use on the service and start "texting" with your friends!
Please note: if you use an Android tablet with support for voice calls and you have a SIM inserted in the device, you can activate WhatsApp normally as if it were a smartphone, but clearly you will have to use the number of the SIM inserted in the tablet and not that of your mobile phone (therefore you will have two separate accounts).
WhatsApp for iPad
If you have an iPad, to use WhatsApp you must necessarily unlock your device by jailbreak and install a tweak, that is a small program, which enables the operation of the service on tablets.
Therefore, proceed to jailbreak iPad by following the instructions in my guide on the subject (be sure to use the most suitable tool for the version of iOS installed on your tablet), download the tweak WhatsPad from Cydia (the alternative app store that is installed with the jailbreak) and proceed with the installation of WhatsApp.
To install WhatsApp on the iPad, you must first download the application on an iPhone associated with the same Apple ID as the iPad (normally via the App Store), then you must backup the device on the computer using iTunes and you must install the .ipa package of WhatsApp on iPad using an application called iFunBox.
You will find explained all the steps to be taken, in great detail, in my guide on how to install WhatsApp on iPad, but I warn you: it is an extremely long and complicated procedure. Furthermore, by activating WhatsApp with the same phone number as your iPhone, you will lose the opportunity to use the application on the "iPhone by".
In short, if I were you I would mainly orient myself on the use of WhatsApp Web from the iPad (through special apps or via browser) and I would consider the actual installation of WhatsApp on the iPad only in cases of real need (or for fun , if you love to "fiddle" with technological devices). Then don't tell me I didn't warn you!