The company – a pioneer of the freemium model of giving away its basic software and selling additional capabilities- added 640,000 paying customers in the period.
Shares in Avast, which joined the FTSE 100 index in June and touched an all-time high of 604.5 pence last month, were trading 5% lower in early deals at 569 pence.
Chief Executive Ondrej Vlcek said Avast performed strongly in the half, aided by increased demand for its anti-virus, privacy and performance software driven by people working from home during the COVID-19 pandemic.
“We are especially pleased by the increase in new customers,” he said. “We now have over 13 million paying customers on the desktop platform.”
Vlcek said the company now expected its organic revenue to grow at the upper end of its previously stated mid-single digit percentage range for the full year.
The strength in desktop, which counts for 79% of the group’s billings, was partially offset by the impact of the pandemic on other parts of the business, including reduced demand from mobile operators for its security software.
The company said adjusted core earnings for the first half rose 2.1% to $241.4 million, beating analyst expectations of $237.3 million, on revenue up 6.6% on an organic basis to $433.1 million, also slightly head of expectations.