Facebook, which has its second largest userbase in India, activated the feature to allow people mark themselves as "safe" from the floods.
Once the user clicks "Yes, let my friends know," the tool automatically notifies his/her Facebook friends. Google has also posted a link on its homepage called 'Resources for the Chennai floods', which provides details about relief camps and updates people about the situation in the city.
Chennai residents have been tormented by the heavy downpour of the last three days with excessive discharge of water last night from Chembarambakkam lake on the outskirts, flooding new areas in the city.
People are using platforms like Facebook and Twitter to not just let people know they are safe but also to helping connect people get to safer locations.
#ChennaiFloods remained as one of the top trend hashtags in India on Twitter through the day.
A website, chennairains.org, has put out a list of places that are offering accommodation and food to people affected by rains.
Telecom operators have also come forward to help people offering free talktime and data usage to help them stay connected.
Sistema Shyam TeleServices Ltd (SSTL) today said it will provide 1GB of free data upload with three days of validity to its prepaid and postpaid customers in Tamil Nadu circle.