Integral Ad Sciences, the US ad tech firm, has revealed it has raised a total of $67m following a fundraising drive.

The company, which specialises in ad viewability and fraud, will invest the funds in advancing its technology and accelerating its global expansion.

The funding round, led by Sapphire Ventures, raised $27m, with investors including August Capital, Pelion Venture Partners and Atlas Venture. It has also secured a $40m debt facility from Silicon Valley Bank.

The company doubled in size in 2014, and anticipates doing the same this year. It opened offices in Paris and Tokyo earlier this month, taking its global total to 11 offices.

“It has been a tremendous year for Integral Ad Science, but our work is not finished,” said Scott Knoll, chief executive of Integral Ad Science. “The expertise in marketing tech that Sapphire Ventures brings to the table makes this partnership especially exciting for us. This will undoubtedly help shape the future of Integral Ad Science and the impact we make on the industry as a whole.”

Following the fundraising, Nino Marakovic, CEO and managing director of Sapphire Ventures, joins the Integral Ad Science board.

“In today’s digital age, the problem isn’t only attribution of ad spend, but also the quality of each impression,” said Marakovic.

“Integral Ad Science is the clear global leader across all digital channels at tackling this problem, and is in a unique position to influence how ads are bought and sold. With a promising future, Integral Ad Science is a strong addition to the Sapphire Ventures portfolio.”