[1] It will have a length of approximately 26 kilometers (16 mi) and will consist of 23 stations, linking Wilanów with Tarchomin.

[2] The line will be an important element of the metro network and the overall transport system in Warsaw.

[4] It will connect the districts of Białołęka, Bielany, Żoliborz, Śródmieście, Wola, Ochota, Włochy, Mokotów, and Wilanów, as well as enable interchange to M1, M2, M3, and M5 metro lines and the main public transport lines: trams, buses, and railways.

[1] On March 14, 2024, Warsaw City Council allocated 56 million PLN for pre-design works for the M4 line.

[14] The initial station plan for the line was shared on the Warsaw Metro website:[2]