Avast lowered its share price when it floated on the London Stock Exchange (LSE) this morning, but is still ranked as one of London's top five tech IPOs, with a valuation of £2.4bn.
The cybersecurity vendor announced plans to go public last month, initially valuing its shares between 250p and 320p.
Shares were trading conditionally this morning at the bottom end of the guidance, with full trading expected to start on 15 May.
The LSE said that Avast's listing makes it "one of the five largest IPOs of all time" in London, as well as the largest in Europe this year.
Cybersecurity rival Sophos made the biggest IPO for a UK software company in 2015, when it listed on the LSE for £1.1bn.
Vincent Steckler, CEO of Avast, said he was proud of the fact that the company is the largest European tech IPO of the year and called its floating on the LSE a "significant milestone".
"As the number of cyberthreats around the world continues to dramatically increase, our focus on developing award-winning security products to help protect people's digital lives has enabled us to grow our business into the number one global consumer cybersecurity company, with more than 435 million users worldwide," he stated.
This is not the Czech Republic-based company's first attempt at an IPO. In 2012 it made a failed bid to float on the Nasdaq, which it blamed on "tough market conditions."
Avast said it plans to use the proceeds raised from the listing to reduce its debt.
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