A gloomy market for technology floats will hang over software maker Atlassian's pursuit of a blockbuster $US3.6 billion ($5 billion) company valuation this week, but strong appetite for new shares from existing investors and its profitable track record should support the planned float.

Former University of NSW classmates turned Atlassian founders Mike Cannon-Brookes and Scott Farquhar, alongside their Wall Street advisers, are expected to front investors after the technology firm filed a US prospectus on Friday revealing it is aiming to sell $US350 million worth of new shares.