How Do Air Fryers Actually Work?

The mechanism, plainly

An air fryer has two working parts: a heating element and a fan. The element gets hot, the fan blows that hot air rapidly around a perforated basket or a rack, and the moving air cooks the food's surface fast enough to brown and crisp it before the inside overcooks. That is the entire machine. It does not fry, there is no oil bath, and the “fry” in the name is describing the result — crisp — not the method.

Why moving air crisps

When hot air sits still against a wet surface, it forms a thin insulating layer — cooler and more humid than the air a few millimeters away — that slows both heat transfer and drying. A fan strips that layer off continuously and replaces it with fresh hot air. So the surface dries and browns faster, which is exactly the texture deep-frying produces by surrounding food in hot oil. Same crisp outcome, different mechanism, no oil.

This is also why the basket has holes and why a rack lets air under the food: the crisping depends on air reaching every surface. Lay food flat in a solid pan and the underside steams instead of crisping. It is the airflow, not the appliance, doing the work.

What follows from this one fact

Almost every other question in the category answers itself once you know an air fryer is a small convection oven:

• Why is it faster than my oven? Smaller cavity, less air to heat, and a fan that transfers heat quickly. Which also makes it cheaper to run.
• Can my convection oven do it? Yes — it is the same technology. Turn on convection and use a perforated tray.
• Is it healthier than frying? It uses far less oil for a similar crisp, because the crisping comes from hot air rather than an oil bath. The health question in full.
• Why do the presets barely differ? Because most of them are the same element and fan at different temperatures and times.

If you take one thing from this site, take this: you are choosing a small convection oven, and everything the marketing calls a feature is a variation on a fan and an element. That frame turns the whole category from a wall of jargon into a short list of things you can actually measure.