From 26 March, the broadcaster will offer a free seven-day catch-up for all its programming via broadband, with so called pre-roll ads to run before the shows.
Viewers will have to sit through two 30-second spots and a short 4oD ident when the strategy launches, days before ITV is due to launch its own broadband TV.
C4 said programme sponsors would also be given the opportunity to extend their on-air association with a 10-second sponsorship clip played immediately before programmes start, although it has not revealed what they will have to pay.
Channel 4 launched its video-on-demand service in December as a mainly pay-per-view offering, despite widespread doubts over whether viewers would spend enough money on downloads to make it viable.
However, the latest move is not a complete U-turn.
The broadcaster's premium US imports and its C4 archive, featuring thousands of hours of programmes such as Queer As Folk, Trigger Happy TV and Drop The Dead Donkey, will remain available on a pay-per-view basis with single, advertising-free episodes available to download for 99p.
Chief executive Andy Duncan claimed C4 was a "pioneer" in the field and admitted it was still experimenting with a range of business models.
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