Researchers have introduced a fundamental principle governing entanglement harvesting, revealing that the amount of entanglement two localized detectors can extract from a quantum field depends on the field's spectral density localization. This principle is demonstrated through an analytically solvable model, where two qubits interact with a leaky single-mode cavity connected to a continuous electromagnetic bath. The findings suggest that the effective spectral density of the field plays a crucial role in determining the entanglement that can be harvested. By understanding this principle, scientists can better design and optimize systems for entanglement extraction, which is essential for quantum computing and quantum cryptography applications. The discovery of this principle has significant implications for the development of quantum technologies, as it provides a new framework for understanding and manipulating entanglement1. This matters to practitioners because it can inform the design of more efficient quantum computing and cryptography systems, potentially leading to breakthroughs in secure communication and computation.