The firm, which had previously tapped investors for only $3.2m, announced the round a year ago, but did not disclose the size at the time, said TechCrunch.
The round was also supported by Bain Venture Partners and existing investors Battery Ventures, InterWest Partners and Google Ventures.
Omtimizely has seen revenue growth of 400 per cent annually to “the double-digit millions”.
The website has won some prominent clients including both the Obama and Romney presidential campaigns last year.
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