NEW YORK — Shares of the digital file storage company Dropbox soared Friday in their stock market debut.

The stock rose $7.48, or 35.6 percent, to close Friday at $28.48 in its first day of trading on Nasdaq. It had climbed as high as $31.60 during the day.

The San Francisco company offered about 26.8 million shares of stock at $21 apiece, while selling shareholders were offering about 9.2 million shares. It had expected to price the shares in a range of $18 to $20.

The company, founded 11 years ago, boasts about 500 million users. It provides services for backing up documents, photos and video. It competes with smaller rival Box Inc., which went public two years ago, as well as technology behemoths Google, Microsoft and Amazon.