As the United States prepares to hold an election during a pandemic, the country is expecting an unprecedented number of people to vote by mail as states move to make it easier for people to vote without going to an in-person polling place. 

Rules and procedures vary from state-to-state, with some sending actual ballots to every registered voter, some states sending people absentee ballot applications rather than the ballots themselves and other states requiring people to go online or to an election office to get an absentee ballot application. Some states before 2020 already ran universal mail-in elections quite successfully. 

Deadlines for ballots to applied for and sent and received by election officials also vary by state. 

WHAT'S THE DIFFERENCE BETWEEN ABSENTEE VOTING AND UNIVERSAL VOTE BY MAIL? 

Below is an overview of states that either this year or previously have moved to the two most permissive forms of mail balloting -- universal mail-in voting and sending absentee ballots applications to all voters. 

Universal mail-in states

Nevada passed a bill earlier this year to become a universal mail-in state. Learn more here.

New Jersey Gov. Phil Murphy issued an order in August making New Jersey a universal mail-in election state. Learn more here. 

California Gov. Gavin Newsom issued an order in May making California a universal mail-in election state and later passed legislation codifying the plan. Learn more here. 

Colorado has had universal mail-in elections since 2013. Learn more here. 

Oregon was the first state in the country to move to universal mail-in elections 20 years ago. Learn more here.

Utah allows counties to opt-in to universal mail-in elections, and every one will do so in 2020. Learn more here

Washington, D.C. announced earlier this year that it would hold a universal mail-in election on Nov. 3. Learn more here.

Washington State moved to its current universal mail-in election system in 2011. Learn more here.

Hawaii in 2019 passed a bill to hold universal mail-in elections. Learn more here.

Vermont Secretary of State Jim Condos issued a directive in late July that Vermont would hold a universal mail-in election. Learn more here.

Montana is allowing individual counties to opt into universal mail-in voting. Learn more here.

States sending all voters absentee ballot applications

Minnesota Secretary of State Steve Simon in September sent absentee ballot applications to all registered voters. Learn more here.

South Dakota Secretary of State Steve Barnett sent absentee ballot applications to all voters earlier this year on which they could have requested absentee ballots for the primary election, the Nov. 3 general election or both. Learn more here.

Wyoming Secretary of State Edward Buchanan in June sent all voters absentee ballot requests that they could return to their county clerks with requests for absentee ballots in the primary election, the general election, or both. Learn more here.

Illinois in July sent mail ballot applications to all Illinois voters who'd voted since the 2018 general election. Learn more here.

Delaware in June passed legislation to allow no-excuse absentee voting and the state mailed applications to all voters. Learn more here.

Connecticut sent voters ballot applications between Sept. 8 and Sept. 11. Learn more here.

Maryland Gov. Larry Hogan earlier this year ordered the state board of elections to send all voters ballot applications. Learn more here.

Ohio has mailed all voters absentee ballot applications since 2012. Learn more here.

Michigan Secretary of State Jocelyn Benson announced in May that all voters would be mailed absentee ballot applications. Learn more here.

Iowa Secretary of State Paul Pate announced earlier this year that his office would mail absentee ballot request forms to all voters. Learn more here.

Wisconsin on Sept. 1 sent mailers that included ballot request forms to roughly 2.6 million registered voters who had not already submitted requests. Learn more here.

CLICK HERE TO GET THE FOX NEWS APP

Rhode Island Secretary of State Nellie Gorbea announced in September that her office would send absentee ballot applications to all voters. Learn more here. 

Nebraska Secretary of State Bob Evnen said in August that the state would mail early ballot requests for mail-in ballots to all voters. Learn more here.

Massachusetts passed a new law in response to the coronavirus pandemic allowing no-excuse mail voting and mailing ballot application forms to everyone who had been registered to vote in the state before July 1, 2020. Learn more here.

Fox News' Morgan Phillips and Ronn Blitzer, as well as The Associated Press, contributed to this report.