SpaceCatalog.org is a non-commercial project creating an open, searchable catalog of objects in the sky. It brings together information from 23 source catalogs, with more than 227,000 indexed objects and over 60 million sky sources. Visitors can explore stars, planets, exoplanets, galaxies, black holes, nebulae, moons, asteroids, comets, and other celestial objects across 88 regions of the sky.

The site offers browsable object records, ranked lists, and established catalogues such as Messier and Caldwell. Users can compare objects by qualities including distance, brightness, size, and discovery date, or explore featured entries with classifications and scientific measurements. A sky map, solar system information, satellite listings, an elements section, and an observing calendar provide additional ways to learn about and visualize the night sky, including current visibility and upcoming celestial events.

SpaceCatalog.org also provides an open API for research and education. It supports catalog filtering, designation lookups, and queries about objects above a user’s horizon. The API is available without a key or account and allows cross-origin requests.