According to WhatsApp, you can't install and use its instant-messaging service on a Wi-Fi-only tablet. Yes, you can. Here we show you how to use WhatsApp on an iPad or an Android tablet with no 3G or 4G connectivity. Also see: Android Advisor
Updated 22 January: As of today Android users can benefit from WhatsApp on the web, which lets them sync their WhatsApp account on their phone with their PC, laptop or tablet via the Chrome browser. See how to get WhatsApp on your phone, tablet, laptop AND PC for more details, or read on for advice on how to physically install the WhatsApp app on your Android tablet or iPad.
How to install WhatsApp on an iPad
The process of installing WhatsApp on an iPad and an Android tablet is very different. With an iPad you need to download the app to your Mac or PC, then use iFunBox to install it on your iPad. For detailed instructions on how to install WhatsApp on an iPad, head over to our sister site Macworld: 'How to install WhatsApp on iPad'.
How to install WhatsApp on an Android tablet
Below we'll concentrate on how to install WhatsApp on an Android tablet with no cellular connectivity, and then how to bypass WhatsApp's phone verification system.
How to install WhatsApp on a tablet: Download the WhatsApp APK file
If you're browsing Google Play on a Wi-Fi-only tablet WhatsApp won't be presented in the search results because it's not officially supported on your device. To get around this you simply need to download and install the WhatsApp APK file - just Google 'WhatsApp APK' and you'll find loads of download sites. Also see: 25 best tablets 2014
How to install WhatsApp on a tablet: Tweak your security settings
Before your Android tablet will allow you to install the WhatsApp APK file you've just downloaded you'll need to enter your tablet's Settings menu, scroll down to and select Security, then enable Unknown sources under Device Administration.You can go back and disable this option once you've installed WhatsApp. Also see: How to add Flash to Android, including Android KitKat
You should now be able to simply click on the WhatsApp APK file-download notification in your tablet's notification bar, then click Install. Once the app is installed press Open.
How to install WhatsApp on a tablet: Bypass WhatsApp phone verification
The next challenge is to bypass WhatsApp's phone verification system. Enter your usual phone number, then click OK. You will receive a text message on your phone, but of course it won't be detected on your tablet.
After five minutes WhatsApp will report that SMS verification has failed and you should try voice verification. Tap Call me, then answer the phone call on your smartphone to get the verification code you need.
You can now enter this code on your tablet and get started using WhatsApp.
Note that WhatsApp will ask whether you want to restore your message history from its backup, but this didn't work for us - presumably because none of that data is stored on the tablet.
How to install WhatsApp on a tablet: Using WhatsApp on a phone and a tablet at the same time
The only real down side to this method of installing WhatsApp on a Wi-Fi-only tablet is that as soon as you verify your account on the tablet WhatsApp will stop working on your smartphone. That's because a phone number can only ever be associated with one WhatsApp account. This might not bother you - after all, you don't really need to view your messages on both your phone and your tablet, and you could simply verify the service on whichever device you'll have to hand that day.
However, you can get around this and use WhatsApp on a phone and a tablet at the same time by using a different mobile number. If you have a second mobile number used for business then you're laughing (also see: Best dual-SIM smartphones). You could also take advantage of the free PAYG SIMs routinely offered by UK mobile operators, although these will expire after a few months if you don't use them, and as soon as someone else registers that same number with WhatsApp you'll have to start over.
It doesn't matter which number you use for verification, as long as it is a mobile (rather than landline) number and that you have it to hand in order to answer the call and get the code.
If you live in the US it has been suggested that you can use a Google Voice number. I'm unable to verify this, since only members with full accounts can receive calls using Google Voice, and that service isn't available in the UK. If this works for you, please let other readers know in the comments section below.
Another one for US readers is TextPlus, a free Android app that lets you send and receive texts and make phone calls on a tablet. Just send your phone a text from the tablet to find out what phone number you need to enter into WhatsApp. Again, however, as I'm in the UK I can't verify this one.
You could also try a service that creates a disposable alias to your mobile number. There are a few free versions out there, but the two Android apps we tried created US numbers that weren't recognised by WhatsApp.