The feature, called AutoRip, was launched in January for CDs. The company has said it has boosted music sales. Digital songs are stored in the customer's online storage account with Amazon. Songs received this way don't count against that customer's storage limit.
The new offer, announced Wednesday, extends to any physical albums bought on Amazon since 1998.
The digital songs can be played on a variety of devices, including Amazon.com Inc.'s Kindle Fire tablets, Android phones and tablets, and Apple Inc.'s iPads and iPhones.