NEMOH is developed to solve potential flow problems using the boundary element method for computing wave loads on offshore structures. The solver solves the first-order problem in the frequency domain. An extended module enables computation of the second-order loads on a structure in bi-chromatic bi-directional waves. NEMOH is released as open-source, developed, and distributed under the terms of GNU General Public License (GPLv3). Along with the source code, a user manual is available which facilitates the compilation and execution of the source files. In this new release, NEMOH v3.0 has new features; irregular frequencies removal method, new linear system solvers for enhancing computational efficiency, and a new module for computing the full quadratic transfer function (QTF) of drift forces. Verification cases are shown for a truncated cylinder, a truncated cylinder with a thin heave plate, a spar buoy platform (SOFTWIND), and a semi-submersible platform (OC4). The results are compared with reference data from commercial software, WAMIT, DIODORE, and HYDROSTAR, and the comparison showed that NEMOH v3.0 is accurate and efficient.