To capture the White House, a candidate must amass at least 270 votes in the Electoral College. Edison Research gave Biden a 253-214 lead over the incumbent.
Here is the state of play in the five states. The vote counts are supplied by Edison Research.
PENNSYLVANIA (20 electoral votes)
Biden has a lead of 14,716 votes, or a 0.2 percentage point margin, as of 4 p.m. ET (2100 GMT) Friday, with 96% of the estimated vote counted. Under Pennsylvania law, a recount is automatic if the margin of victory is less than or equal to 0.5 percentage point of the total vote.
There are still ballots to be counted from Philadelphia, the state's largest city, and Allegheny county, home to Pittsburgh. The majority of ballots left in Philadelphia are provisional and military ballots, Pennsylvania's election commissioner said, adding the final count could take several days.
Friday is the last day that Pennsylvania can accept mail-in ballots postmarked on or before Election Day.
GEORGIA (16 electoral votes)
Biden is ahead of Trump by 1,564 votes as of 4 p.m. ET (2100 GMT) Friday, with 99% of votes counted. Trump needs both Pennsylvania and Georgia to win a second term.
Brad Raffensperger, Georgia's secretary of state, said he expects the margin to be just a few thousand votes, which would trigger an automatic recount. A recount must wait until Georgia's results are certified, expected on or before Nov. 20.
About 9,000 military and overseas ballots were still outstanding and could be accepted if they arrive on Friday as long as they were postmarked Tuesday or earlier.
ARIZONA (11 electoral votes)
Biden has 49.9% versus Trump at 48.6%, a lead of 39,769 votes, with 94% of the expected vote tallied as of 4 p.m. (2100 GMT).
The state has about 250,000 to 270,000 ballots left to count and will give an update at around 9 p.m. ET on Friday, Arizona Secretary of State Katie Hobbs told CNN.
NEVADA (6 electoral votes)
Biden led Trump by 20,137 votes, or 1.6 percentage points, with about 92% of the vote counted.
The state's biggest county, Clark, which includes Las Vegas, has 63,000 ballots remaining to be counted. The next update of the vote count is expected at around 7 p.m. ET (0000 GMT) and the majority of mail-in ballots is expected to be counted by Sunday.
NORTH CAROLINA (15 electoral votes)
Trump led by 76,737 votes, or 1.4 points, with about 95% of the estimated vote counted.
State officials have said a full result would not be known until next week. The state allows mail-in ballots postmarked by Tuesday to be counted if they are received by Nov. 12.