Automatic Visa Revalidation allows F and J status holders to visit Canada, Mexico, and adjacent islands (other than Cuba) for a short period of time (less than 30 days) and re-enter the U.S. with an expired visa.
Students can find details for eligibility and procedures at the CBP website here and at the U.S. Department of State website here.
It is important to review all eligibility requirements before traveling under these conditions. Please note that you are not eligible for Automatic Visa Revalidation if you apply for a visa during your stay and are denied.