CPT is work authorization that allows F-1 students to engage in off-campus employment that is an integral part of their academic program, such as internships or co-ops, and must be completed before graduation. OPT allows students to work up to 12 months in the U.S. in a job related to their field of study, either before or after graduation. Most students choose post-completion OPT, which allows them to work full-time in the U.S. after finishing their degree.