B Lab is a nonprofit organization that is dedicated to promoting and supporting a new type of corporation called a B Corporation, also known as a Benefit Corporation. B Lab was founded in 2006 and is headquartered in Berwyn, Pennsylvania.

B Lab's mission is to create a global movement of businesses that are dedicated to using the power of business to solve social and environmental problems. B Lab provides a framework for businesses to measure and manage their social and environmental impact, and also certifies companies that meet rigorous standards of social and environmental performance, transparency, and accountability.

To become certified as a B Corporation, companies must complete a rigorous assessment process that evaluates their impact on workers, customers, community, and the environment. Companies must achieve a minimum score on the assessment and also meet legal requirements related to their commitment to social and environmental responsibility.

B Lab also provides resources and support to B Corporations, including access to a community of like-minded businesses, best practices for sustainability and social impact reporting, and tools for measuring and managing impact.

Overall, B Lab plays a critical role in promoting and supporting the growth of the B Corporation movement. Its certification process and resources help businesses to align their values with their business practices, and to use their business as a force for good.