Don't try to smell through the can.

You can’t reliably tell if canned tuna has gone bad without opening it. The whole point of a can is to seal in the food and seal out spoilage indicators like smell, gas, and bacteria—until you break that seal, you’re guessing.

What you can check: look for bulging (that’s gas buildup = botulism risk), heavy rust, or dents that broke the seal. If the can is dented along the seam or has a pinhole leak, toss it. Also, trust the expiration date—canned tuna stays safe for years past it, but after a certain point quality drops.

When you finally open it, trust your senses. If it smells sour, fishy in a bad way, or looks discolored (beyond normal dark spots), don’t eat it. If it smells like tuna and looks fine, you’re good.

Your nose is smarter than your eyes here.