More than 4 billion people around the world are still not connected to the Internet.

A new UN report on global access to broadband finds that 57 percent of the world, or 4 billion people, remains unconnected. In developing countries, only about 35 percent of people have Internet access.

As a result, "Internet user penetration in the developing world is unlikely to achieve the Broadband Commission target of 50 percent before 2020," the report said.

Overall, according to the Broadband Commission, about 3.2 billion people (43.4 percent of the world's population) will be online by the end of 2015, up from 2.9 billion last year.

When it comes to developing countries with the highest percentage of households with Internet access, the Republic of Korea ranks No. 1 in the world, with 98.5 percent of homes connected. Qatar is No. 2 at 98 percent, followed by Saudi Arabia (94 percent), and the United Arab Emirates (90.1). Singapore, Oman, Macao in China, Hong Kong, and Bahrain round out the top 10.

"Countries need to adopt effective policies and strategies to make broadband available, affordable, and accessible, as a vital enabler of sustainable development in modern-day knowledge societies," the report said. "It is increasingly vital to extend access to digital education services, new capabilities, culture, entertainment, healthcare, financial and commercial services, along with training and education."

Cellular gains have decelerated, as well: Though global mobile subscriptions (connections) will top 7 billion this year, the total number of unique mobile subscribers (people) actually sits somewhere between 3.7 and 5 billion.

Operators in areas with saturated markets—the developed world, mostly—are now focused on migrating customers to 3G and 4G networks, retaining subscribers amidst competition, and investing in foreign markets.

"Among the 4.2 billion people who are not online, many people may be unaware of the Internet's potential or cannot use it, because there is little or no useful content in their native language," the Broadband Commission argued.

"It is vital to improve awareness of the Internet and its content, particularly in languages that are not well-represented online," the report said.

The International Telecommunication Union (ITU) reported similar findings earlier this year.

U.S.-based companies Facebook and Google are also doing their part to increase Internet access around the globe via Internet.org and Project Loon, respectively.