How to do it
Seal the opened bag as tightly as you can. Press out extra air first, roll the top down firmly, and close it with a clip, clamp, or rubber band. Put the bag in the freezer, preferably flat and away from foods with strong smells.
You can eat the chips straight from the freezer. If you do not like them cold, let a portion sit at room temperature for two to five minutes. Take out only what you plan to eat and put the rest back immediately.
Ingredients
You do not need real ingredients, only the snack and a good way to close the bag. This works well for potato chips, tortilla chips, crackers, pretzels, pita chips, and similar dry, fatty snacks. A tight clip matters more than a fancy container because the goal is to reduce contact with air and moisture.
Why it works
Chips lose their crunch mainly because they absorb moisture from the air. A freezer is cold and relatively dry, so that process slows down. Dry, fatty snacks also do not freeze solid like ice because they contain very little free water.
That makes this trick useful when a large bag is not finished in one sitting or when you have several snack bags open at the same time. Instead of turning stale and soft after a few days, they often stay pleasantly crisp much longer.
Good to know
The freezer will not magically fix chips that already taste old or damp. Use this method right after opening the bag, or at least by the next day. It is not ideal for moist, filled, coated, or chocolate-covered snacks because their texture or surface can suffer.
Also watch out for odors. Chips can pick up freezer smells if the bag is loose or stored beside strong-smelling food. If in doubt, put the clipped bag inside a freezer bag for an extra barrier.