K1 visa (Fiancé(e) visa) allows a foreign-born fiancé(e) to enter the US for 90 days to get married, while CR1 visa (Spouse visa) is for married couples to live together in the US.

K1 visa requires marriage within 90 days of entry, while CR1 visa requires the couple to be already married.

Both visas lead to a Green Card, but K1 visa holders must get married and apply for Adjustment of Status, while CR1 visa holders receive a conditional Green Card upon entry.