[6] The line is colored forest green on system maps.

On 31 December 2012, the ground maintenance warehouse of Jinqiao Parking Lot collapsed during the construction process, resulting in 5 deaths and 18 injuries.

In June 2021 Songjiang's Party secretary announced that a five station 17.3 km (10.7 mi) west extension to Dongjing on line 9 will start construction within the year.

[12] Construction began on 16 December 2022 with six stations planned on the extension, all in Shanghai's Songjiang District.

[13] The trains of Line 12 are composed of 6-carriage of Class A cars, with a design speed of 80 km/h (50 mph), VVVF AC drive, and a design life of 30 years.