The delayed launch, which was originally scheduled to take place on 31 March, has seen Channel 4 win the race to become the first major broadcaster to provide advertising around its video-on-demand service, 4oD.
The ITV service is set to offer more than 1,000 hours of archive content online free of charge. Viewers will also be able to catch up on shows such as Coronation Street within a 30-day window and watch live streamed content from ITV's portfolio of channels.
The ad-funded model already has the backing of clients such as Vodafone and Sony, thanks to a deal with Omnicom's pooled buying operation, Opera.
ITV hopes to boost its online offerings to bring it in line with the rest of the industry.
It has already expanded its ITV Local broadband service to London and central England.