Daniel Ek, Spotify's founder, announced at a press conference in New York yesterday that the service has expanded to include tablets and smartphones, which previously was only available with a Spotify premium subscription.
Ek said the launch was the result of rise in the use of tablets and smartphones in the place of PCs, adding that it "doesn't make sense from a product perspective not to make it free on tablets and phones".
Spotify Free is now available on both Apple's iOS and Google's Android operating systems. It will function as a shuffle option, meaning users can listen to existing playlists or artists' full catalogues on shuffle but not choose individual tracks.
Ads will play every three or four songs in line with the desktop product, but the company is hoping to incorporate native ad formats and location based advertising in its new platforms.
Spotify has also expanded its service to 20 new markets in South America and Eastern Europe, which has increased its reach to 55.
Ek said: "I genuinely believe we're giving people the best free music experience in the history of the smartphone and the tablet, and it's not just for people who subscribe to Spotify Premium.
"There is really no free mobile service like this at all. We are the only team to have the marketing and licensing rights to this around the world."
Ek announced the ad-funded service would work with a new speaker system 'Spotify Connect', which allows users to connect their portable devices to speakers from partners such as Pioneer and Bang and Olufsen on Wi-Fi.
Ek also said that Spotify has exclusively secured the entire back catalogue of legendary rock band Led Zeppelin.
Spotify claims its users stream more than 4.5 billion hours of music a year and more than1.5 million playlists are created on the digital music service every day. Brands including Samsung and McDonalds have advertised on the platform.