A head-mounted display (HMD) includes various features that allow for customizing the HMD to different users. The HMD may include an interpupillary distance (IPD) adjustment mechanism that includes a double biasing assembly for smooth, controlled adjustment of the spacing between lens tubes. The HMD may include a field of view (FOV) adjustment mechanism that includes first and second gear assemblies connected via a connecting rod to allow uniform adjustment of the spacing between the lenses and the user's face. The HMD may further include a swappable face gasket, a swappable visor, a removable head strap, and a modular accessory compartment for further customizations to the HMD. The HMD may further include inconspicuous spectrum-transmissive windows that are made with a spectrum-transmissive base material for the HMD housing that is coated with a spectrum-opaque material, and the spectrum-opaque material is selectively removed to create the spectrum-transmissive windows.