What is a Visa?
A non-immigrant U.S. visa is issued as a stamp in your passport by a U.S. embassy or consulate outside the United States. A visa stamp indicates that you are eligible for entry and reentry to the United States in the immigration category indicated (F-1, J-1, H-1B, TN, etc). Most visa stamps are for multiple entries.
No, it is not possible to apply for or to renew a visa in the United States. Visas are issued only by a U.S. consul in a U.S. embassy or consulate outside the United States.
A visa does not determine how long you can remain in the United States. Therefore, you may stay beyond the expiration date of a visa as long as the visa document (Form I-20, Form DS-2019, or Form I-797) remains valid. Once the proper visa expires it will be necessary to apply for a new visa stamp, through the same process as your initial visa application, at a U.S. embassy or consulate when traveling outside the United States.
The length of the visa, as well as the number of entries allowed, is determined by the U.S. consular officer and by agreements between the U.S. and your country of citizenship. In some cases, one visa will not cover the full length of study, and if this occurs you will need to apply for a new visa on your next visit outside the U.S. after the expiration date.
It is possible for most international visitors to apply for a visa in a country that is not their home country. Be sure to follow all U.S. embassy guidelines for applying, and additional wait time is possible if security checks are needed.
International students and scholars at Yale should use the appropriate visa related to their current activities at Yale (a student visa or a research scholar visa). Use of a "visitor" or "tourist" visa may have serious consequences when used inappropriately.
Your visa indicates that you are eligible to enter the United States in a specific immigration status. A U.S. border official will review your eligibility and authorize your requested immigration status by issuing the Form I-94 (sample card to the left) to show that you have been granted permission to be in the U.S. This small white card is your arrival/departure document and indicates your immigration status and the length of time you may remain inside the United States.
F and J visa holders will see the notation "D/S" on their Forms I-94. D/S stands for "duration of status" and refers back to the expiration date on your immigration document (I-20 or DS-2019).
Scholars with another visa status (such as H-1B or TN) will be given Forms I-94 with actual expiration dates by which time you are expected to leave the United States or apply for an extension of status.
Your immigration status is also indicated on a visa document such as Form I-20, Form DS-2019 or Form I-797:
A sample I-20
A sample DS-2019
A sample I-797
U.S. Department of State