Is In-N-Out's Special Sauce Just Thousand Island Dressing?

In-N-Out's secret menu may not be much of a secret at this point, but it's a different story when it comes to the special sauce that adorns its burgers and every order of animal style fries. To this day, the question remains: what's in the sauce? On the restaurant's website, the only details disclosed are the allergen information, the nutritional value of a burger when the sauce is added to it, and the fact that the recipe has been "unchanged since 1948," the year the first restaurant opened. If you call the customer service line to try to get more information, as one TikToker did, you'll be informed that the ingredients in the sauce are a "trade secret."

Because of similarities in color and taste, many people assume that In-N-Out's burger sauce is simply Thousand Island dressing, i.e. a blend of mayonnaise and ketchup. However, Thousand Island has a thicker consistency and is slightly spicier than In-N-Out sauce. So, the ingredients can't be exactly the same.

In-N-Out clearly doesn't want to reveal the ingredients of its special sauce, but there may be some clues. The allergen information states that the sauce contains eggs, but no milk. This would mean that the creaminess of the sauce likely comes from mayonnaise as opposed to a dairy product. The In-N-Out sauce packet confirms this as well; the label literally says "contains eggs: in mayonnaise."

Most copycat In-N-Out special sauce recipes believe that the other ingredient has to be ketchup, but on an In-N-Out Reddit thread, one customer claims to have once received a batch of under-mixed sauce on their burger, and is confident they saw a streak of tomato paste in there. Either way, everyone seems to agree there's at least some form of tomato in In-N-Out's sauce, whether it be ketchup or tomato paste.

The other main ingredient, according to celebrity chef J. Kenji López-Alt is relish. As the cook shared with Serious Eats, he made the discovery upon straining out a packet of In-N-Out sauce and finding some of the green stuff left behind. As for the other ingredients, it's hard to say for sure, but in most copycat recipes you'll find different ratios of vinegar to add tang and thin out the sauce, and sugar to balance it out.

If you were to ask someone who works at In-N-Out if they know how to make the special sauce, they probably wouldn't be able to tell you either since it isn't made in-house. Employees have said that it comes to the restaurant pre-mixed. Perhaps the only workers that know the recipe are ones who work at the In-N-Out in Baldwin Park, California; the sauce packets share that they are "Packaged by: In-N-Out Burger, Baldwin Park."

Further confirming the secrecy surrounding the recipe, a former In-N-Out cook revealed in a Reddit AMA that, even after seven years working for the company, he was never told the secrets behind it. In response to another comment, the Redditor also shared that In-N-Out wouldn't even let him buy the pre-made sauce in bulk. Either the burger chain is really that secretive over its sauce recipe, or the employees are really good at pretending they don't know how to make it.