Does alcohol content decrease during storage?

Expanded Explanation

If the bottle is well sealed, the alcohol content is generally stable. Ethanol doesn’t “break down” under normal storage conditions, and in a closed system your ABV shouldn’t drift much. Most home liqueurs will taste different over time while remaining essentially the same strength.

ABV can effectively decrease if your container isn’t truly airtight, especially with closures that allow vapor exchange (some corks) or worn gaskets. Heat can worsen this by increasing internal pressure and encouraging micro-leaks; frequent temperature swings are particularly unkind.

If you need confidence, measure your process rather than guessing: calculate ABV after dilution/syrup additions, and keep notes on volumes. For long storage, prefer glass bottles with good caps, store cool and dark, and avoid half-empty bottles for months (headspace encourages oxidation and aroma loss even when ABV stays steady).