Put the French fries in the basket and cook on 400° F (200° C) for 15 minutes, shaking the basket once or twice during cooking. If the fries are not as crispy as you like after 15 minutes, continue cooking in 2 minute increments until your preferred degree of crispiness.
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Notes
If the fries aren't crisping up the way you want, give them a light spray of cooking oil and put them back on for 2-4 more minutes. The oil will help them crisp better.
If after 15 minutes, your fries aren't cooked to your preferred doneness, put them back on for 2-4 more minutes, or until they've reached the crispiness you like.
Make sure to shake the basket at least once during cooking. That will allow all the fries to get air circulating around them.
All air fryers have different wattage and may cook at different rates. You may need to adjust the time or temp for the best results.