Tesco is taking on iTunes with a new music and films download service. Tesco Digital will launch next month with more than three million tracks. 1.6 million of those will be compatible with MP3 players straight away.
It plans for the site to be compatible with iPods by the end of the year.
By then it'll also be offering downloadable films, TV shows and computer games.
Tesco will only say that prices with be "competitive" and prices will vary depending on the album or single tracks.
The chain launched tesco.com in 2000 and was the first major British supermarket to enter the music download market in 2004.
But that service is only available in Windows Media format.
Graham Harris, Tesco's commercial director, said: "We wanted to create an exciting and easy-to-use entertainment shop that Tesco customers of all ages and technical ability can use and trust.
"We're starting out with a comprehensive music offering, but customers can expect downloadable TV and films as well as games to buy very soon.
"It really is a case of watch this space."
As well as food and clothes, the supermarket giant now sells furniture, mobile phones, credit cards, petrol, loans and mortgages.
Tesco confirmed its place as the UK's largest retailer on Tuesday when it announced last year's profits were up to more than £2.8bn.