be common/public knowledge

be common knowledge

To be something that is generally or widely known, whether or not it has been verified or officially recognized. The fact that a healthy diet and regular exercise are the best defense against disease is common knowledge at this point.
See also: common, knowledge

be public knowledge

To be information that is available to anyone (the public) or that is generally or widely known. These reports will all be public knowledge after the trial is over, but for now they must remain secret.
See also: knowledge, public

be common/public ˈknowledge

be something that everyone knows, especially in a particular community or group: What do you mean you’re surprised he’s leaving? I thought it was common knowledge that he was looking for another job!
See also: common, knowledge, public