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3 September 2015 Last updated at 00:40 BST
It is home to hundreds of thousands of people, many of whom have been getting access to smartphones.
Across India, 40 million smartphones are expected to be sold this year alone.
In the slums, they're giving small businesses new ways to sell, as Sameer Hashmi reports from Mumbai.
Watch more reports on Asia Business Report's website
Dharavi is Mumbai's most famous slum, made famous by the film Slumdog Millionaire.