Toilet constantly making a noise
Turn off water to closet. Empty bowl. Thoroughly inspect flapper for nicks; its attachment to the hubs that hold it; and it’s ove,tall condition; then wipe clean the flapper and the housing on which it rests. Check the water fill tube which fits into the upper end of the vertical pipe. Is it damaged? Is it snug? Is it positioned to drain into the vertical tube? Turn water back on - fill water closet. Flush. Fixed?