International Burger Day lands on a simple but surprisingly divisive question: what do you put on it? CivicScience asked Americans to pick their favorite burger condiment, and ketchup came out on top, but the real story lies in how ketchup and mayo fans differ across the board.

Among those with an opinion, ketchup leads at 35%, followed by mayonnaise at 24%, mustard at 18%, and barbecue sauce at 9%. Age shapes the condiment landscape considerably. Ketchup dominates among adults 65 and older at 42%, while mayo is the top choice among adults 30 to 64 at 32% each. Barbecue sauce skews toward the youngest, with 20% of 18- to 29-year-olds reaching for it, compared with just 4% of adults 65 and older. Mustard follows the opposite pattern, preferred by 21% of the 65-plus crowd versus just 11% among younger and middle-aged adults.

What the Ketchup vs. Mayo Divide Reveals Beyond the Bottle

CivicScience cross-referenced condiment preferences with a range of other questions. Here is what the data show when comparing the two most popular choices head-to-head.

Hamburger bun preference: Ketchup fans are classic-bun loyalists, with 56% preferring the classic bun compared to 40% of mayo fans. Mayo fans spread their preferences more widely, with 19% favoring a potato bun versus just 9% of ketchup fans, and 14% preferring a kaiser roll. The condiment divide extends to the bread, holding it all together.

Burger cheese preference: The classic theme holds on to cheese, too. Ketchup fans lean heavily toward American (39%) and cheddar (26%). Mayo fans are more eclectic, with higher rates of swiss (12% vs. 8%), provolone (5% vs. roughly 1%), and a slightly different split on pepper jack. Both groups agree on one thing: American cheese is the top pick overall.

Finishing condiments before they expire: Ketchup fans are more likely to always finish a condiment before it expires (25% vs. 20% of mayo fans). Mayo fans are more likely to never finish one (23% vs. 15%). Given the respective shelf lives involved, this finding may explain itself.

Food adventurousness: Mayo fans are more likely to seek out new foods and beverages, with 18% saying they almost always try new things, compared to just 11% of ketchup fans. Ketchup fans are more likely to say they already know what they like and stick to it (51% vs. 44%). The condiment preferences map neatly onto broader eating philosophies.

Grocery shopping: Ketchup fans enjoy the grocery store more, with 51% saying they love it compared to 43% of mayo fans. Mayo fans are more likely to say they hate it (57% vs. 49%). Whether that reflects a broader attitude toward food routines or just the chore of restocking a refrigerator full of condiments is a question the data leave open.

Planning vs. spontaneity: Ketchup fans skew strongly toward planning, with 56% describing themselves as planners in their day-to-day decisions, compared to 41% of mayo fans. Mayo fans are twice as likely to describe themselves as spontaneous (30% vs. 15%). It is one of the cleanest splits in the data.

Where do you stand? Take this poll now and see how your preference compares with other Americans:

Ketchup and mayo fans are more than just two points on a condiment shelf. Across bun choices, cheese preferences, grocery habits, and how they approach decisions, the two groups paint a consistent picture of two genuinely different kinds of burger eaters and, apparently, two different kinds of people.

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This article’s data comes solely from CivicScience’s database, which contains nearly 700,000 poll questions and 5 billion consumer insights.