Nonimmigrant visas are divided into eighteen main categories, and the number of visas in most categories are not limited. Only a few categories of non-immigrant visas allow their holders work in the United States. Immigrant visas permit their holders to stay in the United States permanently and ultimately to apply for citizenship. An alien who has an immigrant visa is permitted to work in the United States. Congress limits the overall number of immigrant visas, which was 675,000 in 1995.
Many immigrant visas are also subject to per-country caps.