why does bread go stale faster in the fridge than on the counter?

Bread goes stale in the fridge faster because of a process called starch retrogradation.

When bread is baked, starch molecules absorb water and become soft and flexible. As the bread cools and eventually begins to lose moisture, those starch molecules start to recrystallize and harden.

This process happens most rapidly at temperatures between roughly 32°F and 40°F (0°C to 4°C)—exactly the temperature range of your refrigerator. By placing bread in the fridge, you are essentially accelerating the crystallization of the starch, which causes the bread to turn firm and dry much quicker than it would at room temperature.

For the best results:

• Short-term: Keep bread in a bread box or a sealed bag on the counter for a few days.
• Long-term: Freeze the bread. Freezing temperatures essentially "pause" the retrogradation process, keeping the starch molecules from recrystallizing. If you toast or thaw frozen bread, it will return to a texture very close to when it was fresh.