Text from Federal Regulation: 8 C.F.R. § 214.2(f)(6)(i)(G)
For F-1 students enrolled in classes for credit or classroom hours, no more than the equivalent of one class or three credits per session, term, semester, trimester, or quarter may be counted if taken on-line or through distance education in a course that does not require the student's physical attendance for classes, examination or other purposes integral to completion of the class. An on-line or distance education course is a course that is offered principally through the use of television, audio, or computer transmission including open broadcast, closed circuit, cable, microwave, or satellite, audio conferencing, or computer conferencing.
International students on F-1 and J-1 visas are required by Federal Regulations to maintain full-time status (12 hours undergraduate or 9 hours graduate - fall and spring semester; 6 hours –summer semester). They must also make normal progress towards the educational objective listed on their I-20 or DS-2019.
F-1 and J-1 international students can only count ONE online class toward their minimum number of credits as their full-time enrollment during their normal semesters. If a student only needs one course to complete the program of study, the course cannot be online or distance learning.
International students in other visa categories are exempt from this limitation.
An undergraduate student who is required to take 12 credits in the spring and fall to maintain their status may take one 3 credit course online in each semester. If the student enrolls in 15 credit hours, 9 of those credit hours must be taken through traditional classes (on-campus or off-campus), but the additional 6 credit hours may be taken online or through distance learning classes that do not require regular attendance.
A graduate student is required to complete 9 credit hours of graduate level courses in order to maintain the F-1 status. The student must take at least 6 hours through traditional classes and 3 or more additional credits may be online.