The small cruisers of the Kolberg class were significant bigger than their predecessor, enabling to add two additional 10,5 cm guns to the ships. All four ships had different kind of turbines to find the best of them for later cruiser designs: Melms & Pfenninger (Kolberg ), Parsons (Augsburg ), Schneider-Zoelly (Cöln ) and AEG-Curtis (Mainz ). Those installed in the Cöln proofed to be very unreliable therefore they were exchanged with Germania-turbines after trials.

Like many other small cruisers, their main armament was replaced during the war, the twelve 10,5 cm guns were replaced with six 15 cm guns. They were good seagoing ships, but had a bad maneuverability.

Cöln and Mainz were both sunk in the Battle of Helgoland where the German reconnaissance forces were attacked by British battlecruisers.  Mainz was sunk early in the battle after it successfully damaged the destroyers Laurel , Liberty and Laertes . It then was hit by a torpedo disabling the ship. with only one gun left, the Mainz then drifted toward four British cruisers which finally sunk the German ship.