Rdio today announced it is making its music streaming service free on the Web for all US users. In other words, you can access the company’s over 20 million songs, as well as albums, playlists, and stations from any computer without paying a dime.

So, what’s the catch? Rdio says it has added “in-stream messaging” (read: ads) to its Web service. The company explains these will consist of new feature announcements, messages from partner brands, notifications about exclusive content, and “other helpful tips.”

rdio Rdio takes on Spotify with free Web streaming for US users

The announcement comes less than a month after Spotify dropped the remaining time limits that used to govern usage of its Web and desktop apps. Spotify users who were still restricted to just 2.5 hours of music per week — a limit that would come into effect after the six-month “grace period” had passed – can now listen for as long as they please, although they are still subjected to ads. Rdio’s change is limited to the US, where Spotify users have always had unrestricted listening.

Spotify’s paid service is still priced at $9.99 per month, and so is Rdio’s. If you’re already an Rdio Unlimited subscriber, Rdio promises your listening experience will stay exactly the same, meaning you won’t hear any of the aforementioned ads.

That seems to be the price point that almost all subscription music services settle on, plus a free option subsidized with ads to get users hooked. Yet all of these offerings can’t coexist forever: we’re willing to bet 2014 is the year when some of these offerings get killed or acquired.

See also – Beats Music streaming service launching on January 21 for $10 per month and Why Google Play Music All Access beats Spotify hands down

Top Image Credit: Shutterstock / Brisbane