The software, the tenth substantially revised version to be released since the service launched more than a year and a half ago, can read the sonic characteristics of a given song file. Napster can block a file from being traded through its service based on that identifying information.
The company, which licensed this technology from Virginia-based Relatable last month, told visitors to its Web site that it was adding the feature as a way to stay on the right side of a court's order.
"As the technology available for the identification and tracking of music files has evolved extremely rapidly over the past few months, Napster has quickly embraced it in order to better protect copyright holders and improve our users' experience," the company said in a message posted on its Web site.
It also promised future "usability enhancements" based on the identification of individual files, but did not give further details. Other file-swapping services provide the ability to resume stalled downloads or pick the fastest possible download by identifying identical files offered in different places.
It's unclear whether the new feature will be able to go much farther than what Napster has already done to comb out the trading of unauthorized works on its service.
After more than a month of complaints from record labels, the company has strengthened its filters to the point where finding songs from major label artists has become difficult or impossible.