The commercial capital of India saw the Internet user base growing to about 16.4 million in October this year from 12 million in the same month last year, the joint study by the Internet and Mobile Association of India (IAMAI) and IMRB said.
Delhi was second with a user base of 12.1 million. The National Capital recorded the fastest year-on-year growth rate of 50 per cent in Internet user base among top eight cities of the country.
India had about 243 million Internet users as of June 2014, according to IAMAI.
Top eight cities -- Mumbai, Delhi, Kolkata, Bangalore, Chennai, Hyderabad, Ahmedabad and Pune -- accounted for over 58 million Internet users, the study said.
Kolkata ranked third in the list with 6.27 million users, followed by Bangalore (5.99 million) and Chennai (5.58 million).
"Overall, the top four metros have a 23 per cent penetration of Internet users in India. The other four metros have 11 per cent penetration," it said.
Among other cities with a population of more than one million, Surat, Jaipur, Lucknow, Vadodara and Nagpur have the highest number of Internet users.
Surat had 2.97 million users, followed by Jaipur (2.35 million), Lucknow (1.95 million) and Vadodara (1.85 million).