There are several beaches in Karachi opening up to the Arabian Sea that are suitable for running. Our top recommendations:
Clifton Beach. Our favorite beach for running in Karachi. 6 km beach itself is wide, with fairly firm sand, especially near the water. There’s also a ~4 km promenade starting at Beach View park, and additional parks and running paths in the area. At the northern end of the beach, you can run along the Oyster Rocks pier (firm sand surface) for ~1.5 km, with good views of the Oyster Rocks (Access is off Marine Promenade, adjacent to the Clifton Beach Parking Lot).
Sandspit and Manora Beach. Nearly 6 km of beach that’s fairly runnable. Located just south of the Port, off Kakapir Rd.
Hawke’s Beach. Just west of Sandspit Beach. A wide beach, OK for running, though we prefer Sandspit.