In case anybody was actually wondering, the difference is sudsing agent. The manufacturers originally put a chemical in laundry detergent to make more suds. That doesn’t make them clean clothes any better, it’s just for psychological effect. Customers feel like it’s working better when they can see suds.

But too much sudsing in front-loading machines can cause leaking from around the door seals. (Same as putting dish detergent in the dishwasher.) So the HE detergents are the same thing, but without the sudsing agent. They work just fine in top-loading machines, too.

But does anybody remember those TV ads for Biz detergent which pitted a woman using it against man using “Hiz” detergent? Hooray for casual sexism!