Open primaries take a few different forms, but they tend to mean that everyone has the right to vote in the political primaries that apply to their geographic location. In closed primaries, only registered party members can vote in a given primary, which means unaffiliated and independent voters aren’t allowed to vote in these important elections. 

Right now, 27 states hold some form of open primaries, while the remainder hold some form of closed primaries.

• Open primary states include: Alabama, Arkansas, Georgia, Illinois, Indiana, Michigan, Minnesota, Mississippi, Missouri, Montana, North Carolina, Ohio, South Carolina, Tennessee, Texas, Vermont, Virginia, Wisconsin.
• Closed primary states include: Alaska, Arizona, California, Connecticut, Delaware, Florida, Hawaii, Idaho, Kentucky, Maine, Maryland, Nebraska, Nevada, New Jersey, New Mexico, New York, North Dakota (no voter registration), Oklahoma, Oregon, Pennsylvania, South Dakota, Utah, Washington
• States with a partisan primary and partisan voter registration include: Colorado, Iowa, Kansas, Massachusetts, New Hampshire, Rhode Island, West Virginia, Wyoming