Sotheby’s, the auction house that put activist investor Dan Loeb on the board after he battled with management over performance and strategy, entered into a partnership with Ebay Inc. to sell artworks online.

The companies are building a platform for collectors and first-time buyers to browse and purchase collectibles including art, jewelry and fine wine, according to a statement today. Ebay and Sotheby’s will start by offering a number of live auctions taking place at New York-based Sotheby’s, and will offer 18 collecting categories.

Sotheby’s and Ebay are seeking to tap a growing number of customers that are buying art online, with such sales projected to reach $13 billion by 2020, the companies said. Online bidders accounted for 17 percent of the total lots offered in 2013 by Sotheby’s, which in April sold John James Audubon’s The Birds of America for an online record price of $3.5 million.

Billionaire hedge-fund manager Loeb in May joined the board of Sotheby’s following a proxy fight. Loeb’s Third Point LLC is Sotheby’s largest shareholder and for months pushed the auction house to improve what it calls a “deteriorating” competitive position through better use of technology for online sales.

“Sotheby’s sorely lacks innovation and creativity at its most senior levels and requires an infusion of leadership, accountability and transparency,” Loeb wrote to Sotheby’s shareholders April 4.

Sotheby’s rose 1.2 percent to $40.16 at 10:18 a.m. in New York, paring losses this year to 17 percent including reinvested dividends.

“We believe there is a great opportunity, through this partnership, to truly make art more accessible to exponentially more collectors,” Bruno Vinciguerra, Sotheby’s chief operating officer, said in today’s statement.