NetZero was launched in October 1998, founded by Ronald T. Burr (original CEO), Stacy Haitsuka, Marwan Zebian and Harold MacKenzie.

NetZero was the first company to invent real-time URL targeted advertising based on surfing patterns under US patent 6,366,298 [2] Monitoring of Individual Internet Usage.

They claimed to offer free Internet service forever, in exchange for displaying ads, either on a permanent toolbar or on a "banner" that was shown when online.

In addition NetZero acquired AimTV which displayed full video quality 30 second ad spots as well as Simpli and RocketCash.

Users who exceeded 40 hours were directed to the company's "Platinum" service, which provided unlimited access for $9.95 per month.

With the income statement reinvigorated through charging heavier users of the system, NetZero merged with its rival Juno Online Services and created a new holding company, United Online which traded on NASDAQ under the symbol UNTD until Netzero was acquired by B. Riley Financial in July 2016.

In June 2005, the company released a new client that replaced the advertising bar with an Internet Explorer Browser Helper Object.

In addition, the Linux version requires the Java Runtime Environment to be installed prior to use of the NetZero dialer.