We present an experiment test of the effect of the information dissemination channel (public vs. private) and group identity on norm compliance. Prior literature in norms intervention claims that public channels of information dissemination are more effective in increasing norm compliance than privately disseminated information. We identified two possible mechanisms for the effectiveness of public channel on norm compliance: 1) public channel increases certainty about others’ information and turns blind cooperation into coordination under public information, i.e. common knowledge mechanism; or 2) public dissemination lead to group formation, i.e. group identity mechanism. We disentangle the two possible mechanisms in a lab experiment by systematically varying channel of dissemination and group identification, and testing the resulting coordination on a fairness norm on a public good game with heterogeneous endowment. We find that group identity has a significant positive influence on norm-compliant behavior, while public information ambiguously or even negatively affects norm-compliance for participants with low endowment. Our results also have implications for designing public policies oriented to enhance norm compliance.