Surveys in star-forming regions reveal the existence of free-floating planetary-mass objects (PMOs) that have masses that overlap with those of giant exoplanets but do not orbit a star. A detailed spectral characterization of PMOs is lacking due to their intrinsic faintness, significant extinction present in young environments, and, at these low luminosities, considerable contamination coming from background field objects. Nearby young moving groups (ages 15-200 Myr) are useful laboratories as they enable the study of objects that, due to their effective temperatures, will share many spectral properties with younger, planetary-mass objects. In this work, we construct a spectral library of young late-type objects and provide methods for spectral typing and gravity-class assessment. This is important and timely since the upcoming observations with the James Webb Space Telescope will uncover large datasets of spectra from young objects (ages < 5 Myr) in the early-L to late-T spectral type range, which were previously non-detectable.

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