The inauguration was held under the watch of more than 25,000 National Guards, who have transformed the US capital into a garrison city, mainly because of the threat of more violent protests by the supporters of outgoing President Donald Trump, who became the first president to skip his successor's inauguration since Andrew Johnson in 1869.
Outgoing Vice President Mike Pence attended the ceremony.
Biden enters the White House with the top challenge to lift the country from the devastation of a raging pandemic that has killed more than 4,00,000 Americans and thrown millions into economic distress.