Apple has apparently reverted to offering 30-second song previews, as opposed to 90-second ones, on the iTunes Store.

Apple increased the length of song previews from 30 seconds to 90 seconds in December 2010, believing that the extension would lead to more purchases by potential purchases.

But now, as reported by MacRumors, it appears that Apple has brought song previews to their previous duration both on the iTunes Store’s desktop and mobile versions:

For example, previews of all songs on Sia’s new album are only 30 seconds despite all of the songs being longer than the 2 minutes and 30 seconds, a length that used to result in a 90 second preview. Many other popular albums are also demonstrating the same short 30 second previews. Coldplay’s entire discography, for example, has only 30 second previews instead of the 90 seconds of preview time that was previously available.

iTunes Store’s 30-second song preview

While most songs have been limited to 30-second previews, some tracks, including certain songs in Apple’s top charts, remain to have 90-second previews.

According to some iTunes Store customers, the change took effect just a few hours ago. It’s unclear, though, whether the reversion resulted from a system glitch or a licensing issue with record companies.