AT&T on Friday announced a new data-saving feature that'll let wireless subscribers stretch their monthly data allotment by voluntarily electing to reduce the quality of video streamed over the Internet while on a cellular connection.

Stream Saver, as the service is called, will downgrade most high-quality video to standard definition quality (capped at 1.5Mbps, or around 480p / DVD quality) when activated. AT&T says that due to the way some content owners deliver video content, Stream Saver won't be able to detect and "optimize" all video.

AT&T says subscribers will be able to toggle the feature on and off at will without incurring any charges.

Worth noting is the fact that once AT&T activates Stream Saver, it'll be enabled by default for all standard postpaid accounts - even those with "unlimited" data plans - as well as those with GoPhone accounts. Business customers will need to check with their account manager regarding eligibility, AT&T says.

It's unclear at this time how Stream Saver might impact DirecTV subscribers that also use AT&T. In September, AT&T exempted DirecTV from mobile data caps. Just the other day, however, the FCC told AT&T that zero-rating DirecTV from data caps may violate net neutrality rules.

AT&T said it will inform customers once the feature is available early next year and include directions on how to manage it.