WhatsApp has extended its support to two more browsers after its launch on Chrome last month. The web client is now coming to Firefox and Opera browsers.
WhatsApp Web: https://t.co/BPQLxqKDSj – Firefox and Opera browsers are now supported! pic.twitter.com/D4aQiy5IC6
 WhatsApp Inc. (@WhatsApp) February 25, 2015
To connect your web browser to your WhatsApp client, simply open https://web.whatsapp.com in your browser.
You will see a QR code  scan the code inside of WhatsApp, and you’re ready to go.
You have now paired WhatsApp on your phone with the WhatsApp web client.
Your phone needs to stay connected to the internet for the web client to work, and please make sure to install the latest version of WhatsApp on your phone.