A trademark search may be done prior to filing a trademark application to determine if any similar prior trademarks are in force. The USPTO advises applicants to search before filing the application.
A comprehensive search includes searching not only the USPTO records but also looking for common law uses of the mark. It is important to carry out a comprehensive search to identify any conflicting common law rights.
After a trademark application is filed, the USPTO will conduct a search of USPTO records for conflicting marks as part of the official examination process. The official search is not done for the applicant’s benefit, but rather to determine whether the mark applied for can be registered.