According to the United Nations, the numbers will remain concentrated in the developed world, where 80 percent of the population use the net.
According to the UN's International Telecommunications Union (ITU) only about 40 percent in developing countries and less than 15 percent in less-developed countries are online. In several of Africa's poorer and more fragile countries, only one person in 10 is on the internet.
The offline population is female, elderly, less educated, poorer and live in rural areas, said the union, a specialized agency for information and communication technologies.
The UN has a target of 60 percent by 2020. Some 3.9 billion people, more than half the world's population, are not online. ITU expects 3.5 billion people to have access by the end of this year.
Telecoms and internet companies are expanding as more affordable smartphones encourage consumers to browse the internet, causing demand to grow for data-heavy services. However, less developed countries - LDCs - still trail the rest of the world.
It blamed the cost of services and of extending infrastructure to rural and remote customers and the high price of mobile phone use.