The bookmaker saw amounts wagered using its mobile sports app rise by 112% after it was downloaded more than a million times since its launch in February last year. Meanwhile mobile gaming net revenue was up 198%.
Pre-tax earnings for the company before exceptional items were up 4% to £156.2 million while net revenues rose by a fifth to £751.6 million.
Overall online sports revenues were up 44%, driving web operating profits 16% higher to £80.2 million.
Earnings from Hill's more traditional retail business were still the greater portion but the figure of £107.6 million was a 2% fall from the same period last year.
Amounts wagered over the counter were down 5% compared with a period which included the start of the Euro 2012 football tournament.
However net revenues from this area were up by 5%, helped by Hill's best ever Grand National result when 66-1 outside Auroras Encore won at Aintree. Gaming revenue in shops was up 18%.
Chief executive Ralph Topping said: "We have continued the momentum in online, particularly in mobile Sportsbook.
"The shift to mobile sports gaming is an important development and we have invested significant resources in getting the business fully prepared to accelerate this important opportunity.
"With almost 200% growth in mobile gaming net revenue in the first half, this decision is clearly justified."
The 79-year-old business, which employs more than 17,000 people, closed ten shops but opened another 16 over the period, bringing the total to 2,398.
During the period it also launched in Australia, buying Sportingbet's business in the country for £459 million, while it also gained full control of its online business with the buy-out of the outstanding 29% stake for £424 million.