On 25 March 1999 the first test runs began and the line entered service on 16 September 2000 between Taksim and Levent.

On 15 October 2021, it was announced that İBB's free Wi-Fi service had started on rolling stock serving on the line.

The line then heads slightly west just south of Levent through Şişli to historical Taksim Square.

It crosses the Golden Horn towards the Old City and terminates in Yenikapı, a transport hub connecting with M1 line and Marmaray.

(While it was planned to be only a warehouse and operation center in Seyrantepe during the initial construction, it was built as a station to serve both the region and Rams Park.

A future extension southwest of Yenikapı is planned, with five new stations at Kocamustafapaşa, Silivrikapı, Veliefendi, Zeytinburnu and Bakırköy.