It is one of Tokyo's busiest and most important lines, connecting most of Tokyo's major stations and urban centres, including Marunouchi, the Yūrakuchō/Ginza area, Shinagawa, Shibuya, Shinjuku, Ikebukuro, and Ueno, with all but two of its 30 stations connecting to other railway or underground (subway) lines.

Internally JR East refers to the "Yamanote Line" as the quadruple-track 20.6 km (12.8 mi) corridor between Shinagawa and Tabata via Shinjuku.

Trains are put into and taken out of service at Ōsaki (which for timetabling purposes is the line's start and terminus) and sometimes Ikebukuro.

[1][b][c] The daily ridership of the Yamanote Line estimated in a 2015 MLIT National Transit census was about 4 million people per day.

"Yamanote" literally refers to inland, hillier districts or foothills (as distinct from areas close to the sea).

However, a number of technical faults, including problems with door close indicators, resulted in the train being taken out of service the same day.

These trains originally each included two "six-door cars" with six pairs of doors per side and bench seats that were folded up to provide standing room only during the morning peak until 10 a.m. From February 22, 2010, the seats were no longer folded up during the morning peak,[14] and all trains were standardized with newly built four-door cars by 31 August 2011.

The series also had a more modern design and has two 15-inch LCD monitors above each door, one of which is used for displaying silent commercials, news and weather; and another which is used for displaying information on the next stop (in Japanese, English, Korean and more) along with notification of delays on Shinkansen and other railway lines in the greater Tokyo area.

[citation needed] The loop was completed in 1925 with the opening of the double track, electrified section between Kanda and Ueno on 1 November, providing a north–south link via Tokyo Station through the city's business centre.

[citation needed] This policy led to the development of new urban centers (新都心、副都心, shintoshin, fukutoshin) around major transfer points on the Yamanote Line, most notably at Shinjuku and Ikebukuro (which are now the two busiest passenger railway stations in the world).

The area on the west side of the yard made available will be redeveloped with high-rise office buildings, creating an international business center with good connections to the Shinkansen and Haneda Airport.

[23] In October 2022 JR East began performing trial runs for driverless trains on the line aimed to begin sometime in 2028.

Two sets, 17 and 18, were fitted with the new system and re-entered service on the line as train crew conduct ongoing tests on their performance.

^ 「平均通過人員」or average passenger intensity is defined by JR East as Annual passenger-kilometre / route length / number of workdays per year.