Definition

Optional Practical Training (OPT) allows F-1 international students in the U.S. to perform temporary training/employment that is directly related to their major field of study.

There are three types of OPT:

Pre-completion (before completion of academic studies)
Post-completion (after completion of academic studies) and
STEM OPT Extension, which is available to certain students in Science, Technology, Engineering, and Mathematics related fields, as designated by the Department of Homeland Security (DHS)

USCIS Application Form/I-765 codes for the different OPT types
I-765 Code	OPT Type
(c)(3)(A)	Pre-completion OPT
(c)(3)(B)	Post-completion OPT
(c)(3)(C)	STEM OPT Extension

OPT provides temporary work authorization, is not employer specific, and work must be directly related to the student’s major field of study. OPT can also extend a student’s F-1 status for up to 12 months in the case of post-completion OPT, and for an additional 24 months in the case of STEM OPT Extension.