Good beans, poorly stored, taste noticeably worse within days. The fixes are simple and cheap, but they only work if you understand what you're actually protecting the coffee from.
The four enemies
Oxygen oxidises the oils in coffee, dulling flavour over time, the same basic process that turns cut fruit brown.
Light, particularly direct sunlight, accelerates that oxidation and can degrade flavour compounds directly.
Heat speeds up every chemical reaction happening in the beans, including the ones you don't want sped up.
Moisture can trigger staling and, in enough quantity, mould, coffee is porous and readily absorbs ambient humidity.
Doing it properly
Use an airtight container. A container with a one-way valve, which lets CO2 escape without letting oxygen in, is ideal for freshly roasted beans that are still degassing, but any genuinely airtight container is a major improvement over a bag clipped shut.
Keep it opaque or in a dark cupboard. Clear glass jars look appealing but expose beans to light constantly if left on a counter, use an opaque container or store a clear one somewhere dark.
Store at room temperature, not in the fridge. Despite persistent advice to the contrary, refrigerating coffee exposes it to moisture and strong odours from other food, both of which do more harm than the temperature reduction helps. A cool, dry cupboard is the better choice.
Buy only what you'll use in two to three weeks. Coffee is at its best in the weeks after roasting. Buying smaller amounts more often beats buying in bulk and storing it for months, no storage method fully stops the slow decline.
What about freezing
Freezing is genuinely useful, but only for longer-term storage of beans you won't use for weeks, and only if done properly: portion the beans into smaller airtight containers before freezing so you're not repeatedly exposing the whole batch to temperature swings and condensation, and let a portion come fully to room temperature before opening it to avoid moisture forming on the beans.
The takeaway
Coffee storage isn't complicated, it comes down to keeping oxygen, light, heat and moisture away from the beans, buying only what you'll use soon, and not overthinking the fridge question. An airtight, opaque container in a cool cupboard covers nearly everything that matters.
