BERLIN, Germany — Zalando AG, Europe's largest online shoe and fashion retailer, appointed a law firm as it works toward an initial public offering as early as this year, according to people familiar with the matter.

Zalando, based in Berlin, hired Freshfields Bruckhaus Deringer LLP to help prepare for a listing, said the people, asking not to be named as the details aren’t public. The company, which could be valued at more than 4 billion euros ($5.5 billion), has spoken to investment banks, though hasn’t officially mandated advisers, they said.

The timing of an IPO, which may take until 2015, could depend on Zalando’s earnings growth as well as the outlook for online retailing stocks, which have fallen steeply this year. Asos Plc, Zalando’s nearest competitor, has slid 25 percent in London in 2014 after reporting slowing sales growth and saying increased investment will weigh on earnings this year. Ocado Group Plc, the British online grocer, has declined 21 percent.

Zalando could pick Frankfurt over New York as a listing destination, the people said, asking not to be named as the details aren’t finalized yet. Investment banks pitched for mandates earlier this year and advisers including Morgan Stanley and Goldman Sachs Group Inc. are considered most likely to have a role on the IPO, the people said.

Representatives for Zalando and Freshfields declined to comment.

No Decision

Zalando Co-Chief Executive Officer Rubin Ritter said in an interview in February that no decision has been made on an IPO. He conceded that it "can be an option" for the German company, which has been regularly touted by the media as a candidate to list shares, even though it isn't yet profitable.

Zalando is worth about 3.8 billion euros based on the valuation of the 36 percent stake held by Investment AB Kinnevik, a Swedish family-owned holding company that invests in technology companies, according to its 2013 financial statements.

The online retailer’s sales rose more than 50 percent to 1.8 billion euros in 2013, though growth weakened to 36 percent in the fourth quarter, the year’s slowest quarterly increase. Sales and profit margins were affected by unseasonal weather and increased discounting across the fashion industry, according to a Feb. 14 statement. The operating profit margin improved by about 0.5 percentage point from minus 7.2 percent in 2012.

The timing of an IPO could also depend on the performance of technology stocks, which have declined recently amid concern about revenue and earnings growth, the people said. The Nasdaq 100 Index has slumped about 5 percent since reaching a 13-year high on March 5.

That’s also weighed on tech IPOs. Sabre Corp., the travel software and data company that operates the Travelocity website, this week raised less than it planned in its IPO. Weibo Corp., the Chinese microblogging service owned by Sina Corp. and Alibaba Group Holdings Ltd., this week raised $285.6 million in its U.S. initial public offering after pricing the shares at the low end of a marketed range.

By Aaron Kirchfeld, Ruth David, with assistance from Gaurav Panchal and Cecile Vannucci,; Editors: Aaron Kirchfeld, Paul Jarvis