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Direct imaging surveys have revealed a new population of substellar companions with masses around the deuterium burning limit and orbits often farther than 100 AU. The formation of these planetary-mass companions (PMCs) is not fully understood. While core-pebble accretion and dynamical scattering seem unlikely comma disk fragmentation and prestellar core collapse remain to be tested. Simulations have shown that disk fragmentation generally leads to higher mass accretion rates than prestellar core collapse. Therefore comma PMCs are expected to have higher accretion rates than free-floating planets-brown dwarfs if disk fragmentation is the dominant formation channel. Alternatively comma if both populations have indistinguishable accretion rates comma that would suggest a common origin. To test this prediction comma we propose to observe the UV continuum excess and H-alpha emission for PMCs and free-floating objects with WFC3-UVIS multi-band imaging. Our targets are of comparable mass and age comma and have evidence indicative of disks. We will carry out shock modeling and search for any population-level accretion rate differences between the two samples. We will also investigate the empirical relationship between H-alpha line luminosities and accretion luminosities from the stellar-mass toward the planetary-mass regime comma in order to establish whether the mass assembly process for stars comma brown dwarfs comma and planetary-mass objects are analogous and continuous.