1. Install ConnectA2 from Firefox marketplace

ConnectA2 is a mobile instant messaging application, always available in background and compatible with WhatsApp. It can use ConnectA2 network as well as WhatsApp network. You can send instant messages to your contacts for free, send and receive photos, videos and audios, emoticons, if your contacts are using ConnectA2 or Whatsapp apps. You will receive a notification whenever you receive a new message from your contacts.

Marketplace URL : https://marketplace.firefox.com/app/connecta2

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2. Install OpenWapp from Firefox marketplace

OpenWapp is another WhatsApp Client for the Firefox OS. However, it is still new and not as good as ConnectA2, but for those who are not able to use ConnectA2, OpenWapp is a nice alternative. It can also verify and activate your WhatsApp account and you can chat with your friends on WhatsApp. Other supported features include sending emojis, pictures, videos and audio messages. Status can also be changed easily from the settings.

Marketplace URL : https://marketplace.firefox.com/app/openwapp

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3. Install Loqui IM from Firefox marketplace

Loqui Instant Messenger allows you to have all your chat accounts in just one FirefoxOS app. Supports

WhatsApp

Google Hangouts

Facebook Chat

Nimbuzz

Nokia ovi

Microsoft Lync

Marketplace URL : https://marketplace.firefox.com/app/loqui

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