How an air fryer uses convection to create that crispy crunch

• An air fryer is actually a mini convection oven that mimics the effect of frying without tons of oil.
• You can cook almost anything in an air fryer like steaks, cookies, pizza, and french fries.
• Less oil means fewer calories, but that doesn't mean everything made in an air fryer is low-calorie.

You've probably heard of an air fryer. In fact, you probably have friends who are obsessed with theirs. The air fryer has exploded in popularity in the last few years with the promise of perfectly fried food using very little to no oil.

There are so many reasons home cooks love air fryers: They cook food quickly, make great gifts, are easy and safe to use and so much more.

Let's take a look under the hood and get the lowdown on air fryers.

Quick tip: We tested several different air fryers to determine which ones performed the best. Read our guide to the best air fryers.

How does an air fryer work?

Contrary to its name, an air fryer doesn't actually "fry."

"It's a mini-convection oven that cooks food by circulating hot air around it with a fan. This way, food is cooked by convection, which means it can approach the crispiness of fried food while using far less oil. But the intense hot air is also ideal for roasting and even allows you to prepare dishes you might otherwise cook on the grill," says Dan Zuccarello, Executive Food Editor for Cookbooks at America's Test Kitchen.

In practice, what this means is achieving the Maillard reaction from hot air rather than hot oil. The Maillard reaction is what causes food to turn brown and crispy. It's the result of heating sugar and proteins, which is how steaks get that wonderful sear, chips become crisp, and pastries achieve their beautiful golden brown.

In an air fryer, food sits in a perforated or wire basket which ensures all sides of the food make contact with the hot circulating air, cooking it both thoroughly and quickly and crisping along the way.

You'll still need a little oil - that's what the air heats to create the browning. And while you won't get the same level of deep golden brown as you would in a deep fryer, you do get the advantage of quickly cooked food with much less oil and fat hitching a ride.

What are the advantages of an air fryer?

The no-fuss factor is key. Air frying doesn't need constant babysitting since it is set to a timer, has regulated temperature, and automated shut-off. At most, you may need to flip your food halfway through its cooking time or check on things as they approach doneness.

It's a huge time saver. Air fryers been a hit for busy parents (or anyone, really) or for those nights where you don't want to turn the stove or oven on. You can skip heating up your butter or oil altogether.

Food also cooks faster in the air fryer thanks to the compact size and hot air circulation. Because every minute counts in the kitchen when you are short on time.

"The ability to crisp up a batch of chicken nuggets or a couple hand pies, or roast carrots, without embarking on a cooking project makes this a lifesaver for busy parents. We found that we could even create make-ahead freezer simple meals that could be crisped in the air fryer on a moment's notice," says Zuccarello.

Cleaning up is super easy. "The enclosed basket of an air fryer also translates to a clean kitchen - no splattering oil or multiple dirty pots and pans. The baskets are simple to clean: Most are nonstick and dishwasher safe," says Zuccarello.

What can you cook in an air fryer?

When it comes to what you can cook in an air fryer, the possibilities are (almost) endless. But there are certain things that will turn out great and other things better cooked by other methods. These types of foods will turn out great in an air fryer:

• Proteins like chicken, chicken wings, fish, steak, and even hard-boiled eggs.
• Cruciferous vegetables like Brussels sprouts, cauliflower, or broccoli
• Tubers like sweet potatoes and potatoes.
• Leftovers: No more nuking in the microwave where they'll get soggy. Toss in your day-old pizzas or french fries for a revitalizing crisp.
• Some baked goods like cinnamon rolls, cookies, and even cakes can be baked in an air fryer. Air fryers have earned the reputation of adult Easy Bake Ovens, after all.

But there are a few things you may want to steer clear of cooking in an air fryer.

"I'd say don't try to cook anything that needs a lot of liquid to cook, such as uncooked rice. Avoid anything that uses a wet batter that you normally deep fry, like tempura batter, as it will just make a mess," says Michelin star-trained chef Jason Lloyd.

Also shy away from anything that needs to be cooked low and slow, like tough, fatty cuts of meat (think pot roast), shares blogger Laura Miner of Cook at Home Mom.

Ditto to leafy greens (they will dry out), cheese without a base like bread, or things that require soaking, braising, or water absorption.

Is air-fried food healthy?

Using an air fryer instead of deep-frying lowers the calorie count of that food and reduces fat intake, which can reduce the risk of developing heart disease, says nutritionist Sandy Younan Brikho, MDA, RDN.

Because little to no oil is used (as opposed to deep frying foods) the food you cook doesn't absorb as much fat. Weight loss can be a result because of the decreased fat intake and decreased calorie intake, but not everything you cook in an air fryer will be low-calorie.

Insider's takeaway

Air fryers use convection heat - hot air quickly circulated by a fan - to achieve crisp food quickly and with very little oil. They're most well-known as a lower-calorie alternative to deep frying, but they're also wonderful for roasting, reheating leftovers, and getting dinner on the table quickly.