Small emission leak. Loose gas cap, rust on filler neck where gas cap seals, or you top up the tank too much and have damaged the carbon canister and the vent valve does not close all the way.

Mostly related to a worn seal on the gas cap. Look at the seal/gasket on your gas cap. If it is worn/cracked or dirty, the gas cap needs to be replaced.

Try tightening your gas cap or even replacing it.

try google it also

Car wouldn't start, replaced fuel pump, relays and filters and worked like new car. Gas the car up and fuel gauge stuck at half a tank. Took it back to mechanic and they fixed it. Drove it over 300 miles and filled it again halfway during that drive. Very next day turn car on to go gas car up again and check engine light comes on error code p0442.