Update: As of December 9, all 50 states and Washington, DC have certified the results of the presidential election.
On election night, the media uses results that are already in and voter surveys to name winners. Election night calls are largely accurate; however, vote counting goes on for days or weeks after that so that states can get a full vote count. That full count is the official, certified result.
To comply with the timeline of the Electoral College process, all states must reach certified results for presidential and vice-presidential races by December 14 — the day electors cast their ballots. The electoral votes will be counted in a joint session of Congress on January 6, 2021.
According to a statement released on November 12 by a coalition of state and federal election security officials, the 2020 election was “the most secure in American history.” The statement adds that “right now, across the country, election officials are reviewing and double checking the entire election process prior to finalizing the result.” According to the officials, there is no evidence of any compromised voting system in the US this election.