A category K1 visa is a non-immigrant visa granted to a foreign citizen who plans to marry a US citizen within 90 days of entering the US.
With a K1 visa, it is also possible to apply to work immediately after arriving in the US. After the marriage has taken place, the spouse can then apply for a green card. If the intended marriage doesn’t take place within 90 days, the spouse will have to leave the country. Obtaining a K1 visa can take up to six months, and the process includes an interview to prove that the marriage will be legitimate. During the interview, you may be asked some personal questions regarding your relationship such as anniversary dates or how you met one another. Although it can seem a little daunting, the consulate official will just want to know that the marriage is for partnership reasons and not purely to acquire permanent residence in the US.
K3 and 4 visa
K3 and 4 visa types are also a variation of the K1 visa. The K3 visa allows an already married person of a US citizen to join their spouse in the US on a non-immigrant visa. The purpose of this visa is to allow married couples to be united in the US whilst waiting for their application of an immigrant visa to be completed. It is noted on the government website that should a person marry a US citizen out of the US, the visa will need to be applied for in the country of the marriage ceremony.
The children of a person holding a K3 visa will be entitled to a K4 visa. Again, this is a temporary visa allowing a spouse and their children to move to the US until their permanent residence is confirmed by USCIS.