Here we present a state-of-the-art maskless array synthesizer ("MAS 2.0") for ultra-large-scale synthesis of oligonucleotides. Optimized for routine lab use, the device is designed to accommodate any of the largest digital micromirror devices (DMDs) currently available (see Table ), from XGA (1024 × 768) to 4K (4096 x 2160). With an optical relay with a numerical aperture (NA) of 0.12, corresponding to a spatial resolution (Abbe-Rayleigh criterion ) of 1.5 µm at 365 nm, the new synthesizer is able to adequately image the smaller mirror sizes of these DMDs, and has a field of view sufficient for diffraction-limited imaging of even the largest of these DMDs. Additional design considerations included: high optical contrast (scatter minimized) to minimize error rates, high power ultraviolet LED light source (irradiance >100 mW/cm 2 at 365 nm), and very low effort user maintenance . The supplementary documentation linked to this preprint, all with a CC BY 4.0 license is intended to provide all the necessary information to support the construction and operation of the MAS 2.0. This documentation includes the full optical specifications, mechanical drawings, CAD files, part lists, and source code. In addition, the supplementary documentation includes extensive background material on the chemistry and photochemistry for light-directed phosphoramidite chemistry, practical operation of the MAS 2.0, synthesis protocols, and commercial suppliers for necessary hardware and consumables.