Coke Zero vs. Diet Coke: What’s the Difference?

Do Diet Coke have the same ingredients and same flavor? You might be surprised by the results of our research.

Coke Zero vs. Diet Coke: a clash of the titans. Now, I’m an ’80s kid, and for decades, Diet Coke was my beverage of choice. Sorry, Tab—your pink cans were stylish, but the soda was no good. (Find the most popular soda from when you were a kid.)

Diet Coke came out in the summer of 1982, and it was the Star Wars of low-cal drinks, light years better than any other diet beverage. For the first time, a diet soda existed that didn’t remind you that it was low-calorie with every sad sip. I couldn’t imagine Coca-Cola ever making a different diet soda.

But then, in 2005, along came Coke Zero. Someone in the Coca-Cola labs wanted to make a diet drink that tasted more like a full-sugar Coke. Did it work? Do these two beverages really have a different taste or is Coke Zero just a trendy name?

Here’s why the Coca-Cola logo is red—and always will be.

Are Diet Coke and Coke Zero Different?

Diet Coke and Coke Zero both have zero sugar and calories, and the ingredient lists are similar, too. Both consist of carbonated water, caramel color, phosphoric acid, potassium benzoate, aspartame, natural flavors and caffeine (though you can buy caffeine-free versions of both—look for the packaging with gold accents).

Coke Zero has two ingredients Diet Coke lacks: potassium citrate and acesulfame potassium.

And Diet Coke has one ingredient that’s not in Coke Zero: citric acid.

In this interview, Anna Wheeler, health and nutrition manager for Coca-Cola Great Britain, says that “Coca-Cola Zero Sugar looks and tastes more like Coca-Cola Classic, while Diet Coke has a lighter taste because it’s made with a different blend of flavors.”

OK, so that’s what the execs say. But are they right?

Diet Coke vs. Coke Zero Taste Test

I chilled cans of both Diet Coke and Coke Zero, and drank them with no ice, so they wouldn’t be diluted.

Sipping Diet Coke reminds me of what a huge advance it was back in the ’80s. It’s smooth and sweet, and my first thought isn’t, “ugh, yeah, this is a diet soda.” It’s enjoyable, it’s bubbly, it goes well with a meal and is refreshing by itself. I’ve never confused it with a full-sugar Coke, but it’s still a top-notch diet beverage.

Coke Zero was reformulated last summer, and in my Coke Zero review, I wasn’t afraid to say I didn’t love the new formula. I found it almost sour, with a spiciness that older Coke Zero didn’t have. And maybe it’s changed, or maybe I’ve changed, but I didn’t taste that sourness this time. Coke Zero was smoother and sweeter than Diet Coke, and I even found it more bubbly.

Don’t miss our Coke vs. Pepsi taste test!

Which Do We Prefer?

It’s Coke Zero for the win. If a flight attendant or a vending machine gives me the choice, I’ll zero in on Coke Zero every time.

I know cola drinkers who are still mourning the Coke Zero formulation that we lost last year, and I get it. When I first tested the old formula Coke Zero vs. the new one, I vastly preferred the old one. But I can’t live in the past. This Coke Zero is what we have now, and I’ll drink to that.

This is why Coke tastes better at McDonald’s than anywhere else.

Gael Fashingbauer Cooper
Gael has written about food and restaurants for 27 years. At Taste of Home, she dives into taste-testing unusual food products and sharing the latest in food trends and news. She's the co-author of "Whatever Happened to Pudding Pops" and "The Totally Sweet '90s," which celebrate the nostalgic tastes and trends of the '70s, '80s and '90s. As a professional pop culture junkie, Gael has written about TV, movies and books of all kinds for CNET, NBC, MSNBC and "TODAY." If Marathon candy bars ever make a comeback, she'll be first in line.