AtomDB is an atomic database designed for X-ray plasma spectral modeling, primarily used to model collisional plasmas where hot electrons interact with astrophysical elements and ions. It includes fundamental atomic data such as wavelengths, radiative transition rates, and electron collisional excitation rate coefficients, stored in the Astrophysical Plasma Emission Database (APED). The database also incorporates spectral models generated by the Astrophysical Plasma Emission Code (APEC), which calculates spectra for optically thin plasmas in collisional ionization equilibrium. APEC outputs continuum and line emissivity files, enabling separate or combined modeling of emission components. AtomDB is utilized by tools like Sherpa, GUIDE, ISIS, and WebGUIDE to identify emission lines and compare calculated spectra with observational data. The dataset is structured in FITS format for compatibility with CIAO’s Prism tool. While it offers enhanced spectral modeling capabilities, including improved line lists and accurate wavelengths, the database notes that older models like mekal or raymond may sometimes be more suitable depending on specific applications.