A federal judge granted class-action status to Netflix Inc. subscribers in their lawsuit against the company and Wal-Mart Stores Inc. over DVDs.

US District Judge Phyllis Hamilton said that the subscribers bringing suit against the companies in 2009 were “united by common and overlapping issues of fact and law,’’ in an order dated Dec. 23 and filed in federal court in Oakland, Calif.

Wal-Mart and the plaintiffs reached a preliminary settlement of the lawsuit that could pay them as much as $40 million in cash or equivalents, according to a motion filed Dec. 14. A hearing on that motion will be Feb. 9. It doesn’t include Netflix.

The plaintiffs charged that Netflix and Wal-Mart conspired in 2005 to divide the market for selling and renting DVDs to reduce competition. The companies formed an agreement in which Wal-Mart.com would stop renting DVDs online and Netflix wouldn’t offer them for sale.