The *Chandra Source Catalog* (CSC) is a comprehensive resource for X-ray astrophysics, providing detailed and statistically significant studies of X-ray sources detected in imaging observations by the *Chandra X-ray Observatory*. The catalog includes curated, high-quality, and uniformly calibrated positional, spatial, photometric, spectral, and temporal properties of sources, along with science-ready X-ray data products. The CSC Release 2 Series, which includes CSC 2.0 and CSC 2.1, covers a wide range of astrophysical environments and offers enhanced sensitivity and improved algorithms over previous releases. CSC 2.0, published in October 2019, contains 317,167 unique X-ray sources identified in observations up to the end of 2014, while CSC 2.1, published in April 2024, extends this to 407,806 sources, including data up to the end of 2021. The catalog's algorithms have been optimized for better source detection, especially for faint sources, and it now includes a Bayesian X-ray aperture photometry code for robust flux measurements in crowded fields. The current release, CSC 2.1, is tied to the Gaia-CRF3 astrometric reference frame for precise sky positions. The catalog's data products are available from the *Chandra* X-ray Center, facilitating further research and analysis in X-ray astrophysics.The *Chandra Source Catalog* (CSC) is a comprehensive resource for X-ray astrophysics, providing detailed and statistically significant studies of X-ray sources detected in imaging observations by the *Chandra X-ray Observatory*. The catalog includes curated, high-quality, and uniformly calibrated positional, spatial, photometric, spectral, and temporal properties of sources, along with science-ready X-ray data products. The CSC Release 2 Series, which includes CSC 2.0 and CSC 2.1, covers a wide range of astrophysical environments and offers enhanced sensitivity and improved algorithms over previous releases. CSC 2.0, published in October 2019, contains 317,167 unique X-ray sources identified in observations up to the end of 2014, while CSC 2.1, published in April 2024, extends this to 407,806 sources, including data up to the end of 2021. The catalog's algorithms have been optimized for better source detection, especially for faint sources, and it now includes a Bayesian X-ray aperture photometry code for robust flux measurements in crowded fields. The current release, CSC 2.1, is tied to the Gaia-CRF3 astrometric reference frame for precise sky positions. The catalog's data products are available from the *Chandra* X-ray Center, facilitating further research and analysis in X-ray astrophysics.