The BBC's iPlayer now has permission to routinely keep shows available for a year rather than just 30 days, after Ofcom said it could expand its service.
Some shows will be available for even longer, the broadcasting watchdog said.
Ofcom said "the BBC's proposed changes to BBC iPlayer could deliver significant public value over time".
There is likely to be "an adverse impact" on rival services, but that will be outweighed by the public value, the regulator decided.
The BBC will now have to negotiate with independent programme-makers who make many of its shows to formalise the extension beyond 30 days.
The corporation said the decision was "great news", adding: "We'll be able offer so much more to the public."
The regulator added that the change "could increase choice and availability of public-service broadcast content, and help ensure the BBC remains relevant in the face of changing viewing habits".
Ofcom estimated that "the increase in BBC iPlayer viewing could be 14%-24% for general content and 6%-9% for children's content, with an overall increase in BBC iPlayer viewing... of 20%-33%".
The decision follows last month's announcement that shows like Love Island, Gavin & Stacey, Gentleman Jack and Broadchurch will be on ITV and the BBC's new streaming service BritBox when they fall off the broadcasters' catch-up platforms.
The BBC and ITV are joining forces to set up the paid-for subscription service in the UK later this year as a rival to the likes of Netflix.
Ofcom noted that the iPlayer changes could mean "there is likely to be an adverse competition impact on potential new UK-focused subscription services such as BritBox".
But it added that there is "unlikely to be substantial harm to audiences". It also pointed out "ITV's support for the proposals", along with ITV's decision to join forces with the BBC for BritBox.