Why McDonald's Filet-O-Fish Patties Are Square

The Filet-O-Fish is one of McDonald's most popular offerings, alongside the Big Mac and Quarter Pounder. But it has one major difference from these two alternatives beyond what it's made of — the shape. Some have wondered why Mickey D's opted for square filets versus round burgers and chicken sandwiches.

There's no big secret behind the difference, which goes all the way back to the minutes after the fish is caught. In a Facebook post, McDonald's says it processes its Alaska Pollock filets while at sea, which are then frozen into a large block. This is done in an effort to preserve the fish at peak freshness for its long journey to your local fast food location. When the frozen blocks of fish reach the land-based processing plant that turns them into Filet-O-Fish patties, they're sliced into squares to reduce waste and produce the perfect, consistent piece of fish every time.

There are plenty of alternative theories about why the Filet-O-Fish earned its square shape, some of which may be more coincidence than anything else. Reddit commenters suggested square patties help accelerate food preparation in McDonald's fast-paced kitchens. Others suggested the square shape sprang from a desire to optimize shipping and transport to franchises.

Aside from the shape, the Filet-O-Fish is still one of McDonald's most unique offerings, particularly in its origins. Something you may not know about the Filet-O-Fish is that it was invented by a franchise owner in the late 1950s who was seeking an alternative offering for Catholic customers, many of whom avoided eating meat on Fridays. Alongside its classic tangy tartar sauce and half-slice of cheese, McDonald's promotes its Alaska pollock as sustainably sourced within the United States, reflecting steps the chain has taken to preserve sensitive fisheries and lower waste in the catch and processing areas.

Still, it's unquestionably more of a niche item than many other classics from the Golden Arches. See where the Filet-O-Fish stacks up in our list of popular McDonald's menu items, ranked worst to best.