A federal judge in Seattle has allowed a class action lawsuit against Amazon to proceed. The suit claims the online retail giant overcharged hundreds of millions of U.S. consumers. This nationwide class involves 288 million customers and billions of transactions, making it one of the largest ever. The class includes U.S. buyers who purchased five or more new items from third-party sellers on Amazon since May 26, 2017. The consumers allege Amazon violated antitrust law by preventing third-party sellers from offering lower prices on rival platforms. Amazon's policies allegedly enabled inflated fees on sellers, leading to higher prices for shoppers. The company denies any wrongdoing and has appealed the class certification order. Amazon argued the class was too large and that its conduct did not have a widespread effect. The judge found no evidence that the class size was overbroad at this stage. He noted other federal courts have certified similarly large classes.