Music-streaming service Spotify Ltd. says 15 million consumers, roughly a quarter of its user base, pay to listen to music without ads. That’s up 20% from 12.5 million in November and 50% from May.

Spotify offers a free streaming service to consumers willing to listen to ads, as well as a premium, ad-free option that costs $9.99 a month.

Spotify’s jump in paid subscribers was helped by a promotion Spotify launched in December in which it offered consumers a three-month premium subscription for 99 cents. That helped Spotify add 10 million new users over the past two months, growing its customer base 20%—from 50 million in November to 60 million.

The service, which is available in 58 countries, has tripled its user base in a little more than two years. And to help bolster its revenue, Spotify over the past year has rolled out a number of new advertising options. For instance, last fall it introduced a video ad unit that Target Corp. and others have used that lets users listen to 30 minutes of ad-free music if they watch a 15- or 30-second spot.

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