For our latest web performance benchmark we decided to take a look at some popular music streaming sites. There are obviously dozens of websites and applications that allow you to listen to your favorite tunes at anytime and from anywhere so we decided to hone in specifically on those sites that are browser-based. This qualification might have left out a few fan favorites, namely Spotify (though if the rumors are true, Spotify will launch a browser-based version soon, and Apple might not be too far behind). But we thought it would allow us to give the most accurate and comparable round-up of website performance.

So without further ado, the availability and average response times of some of the popular, browser-based music streaming sites this summer were:

Pandora topped the chart as the most reliable choice, with 99.98 percent availability and 3.4 second response times. Jango and MOG followed closely behind with 99.95 percent availability and 3.9 second response times, and 99.85 percent availability and 3.3 percent response times, respectively.

On the other end ranked, Songza, and Slacker Radio. delivered 89.73 percent availability and 9.0 second response times. After digging deeper, we found that the majority of their performance issues came from ads, which might not interfere with the user experience, but do show up in our monitoring.

Songza ranked higher on availability than, but delivered similarly slow response times. This most likely can be attributed to issues with its CDN provider, as well as its reliance on third-party content such as widgets and Facebook.

Slacker Radio started out the summer strong with high availability and fast response times during May and June, but performance degraded heavily in the last two months of the season which impacted its seasonal average.

See for yourself. Below is a graphic representation of Slacker Radio’s website performance between Sept. 11 and Sept. 17. Every purple dot along the X axis represents a fail, where our website check timed out due to a lack of response from the site. The sharp spikes show fluctuation in response time, which on average ranged anywhere from four to 14 seconds. (Labels along the Y axis are in milliseconds.)

As new players emerge in the music streaming space, it will be interesting to see how their performance compares to some of the established market leaders. We’ll be keeping our eyes, ears, and monitors on these sites so we can continue to report on the latest performance trends.

Website performance was measured between May 2012 and August 2012 using Apica’s real browser monitoring. We ran checks on the homepages of these music streaming sites once every 30 minutes from our U.S. West Coast monitoring agent network.