Access the CAS REGISTRY, the world’s most trusted source for accurate chemical substance information. Whether you’re a scientist, manufacturer, regulator, or data scientist, our comprehensive collection provides reliable data to support your work.
![A digital card displaying information about the element nitrogen from the periodic table. It includes the atomic number 7, atomic mass range [14.00643, 14.00728], symbol 'N', and electron configuration [He]2s²2p³. A blue box with white text shows the CAS registry number 7727-37-9.](https://cdn.prod.website-files.com/650861f00f97fe8153979335/68557701f77e4a8e679046f9_d838e484db6befacc157d5154308fe6d_what-is-reg-number.svg)
Chemical compounds are described in many ways, including molecular formulas, chemical structures, generic, systematic, common, and trade names. This lack of clarity can cause frustration, delays, and even safety concerns.
A CAS Registry Number (CAS RN®) is a unique and unambiguous identifier for a specific substance that allows clear communication and, with the help of CAS scientists, links together all available data and research about that substance. Governmental agencies rely on CAS Registry Numbers for substance identification in regulatory applications because they are unique, easily validated, and internationally recognized.
CAS Registry Numbers set the standard for identifying chemical substances since 1965.
For common and frequently regulated chemicals, you can use CAS Common Chemistry, an open community resource with nearly 500,000 chemical substances from CAS REGISTRY.
If you’re looking for a more unique substance, simply complete and submit a CAS Registry Lookup service order form and receive results within 24 hours (excluding weekends and holidays).
If your chemical name or CAS Registry Number matches a record in CAS REGISTRY, a print of that record will be returned with your results.
CAS REGISTRY is the database of disclosed chemical substances curated from scientific literature and other sources. It contains over 290 million substances and is continuously enhanced with new substances and the most up-to-date information for substances in the collection.
CAS Registry Numbers (CAS RNs) are the unique numeric identifiers assigned to chemical substances within the CAS REGISTRY. A CAS RN designates only one substance, ensuring precise identification. They allow for clarity in research across regions and languages and allow CAS databases and solutions to link a wealth of information about specific substances.
![A digital interface displaying the chemical structure of a compound with CAS Registry Number 152342-19-3. Tabs labeled 'Reference (1)', 'Reactions (1)', and 'Supplier (1)' are visible. The compound's formula is C₂₂H₂₃N₃O, and its name is 4H-Pyrrolo[1,2-b]pyridazin-4-acetamide, N-butyl-2-phenyl-.](https://cdn.prod.website-files.com/650861f00f97fe8153979335/685577013343c6ae0554bf34_a204913df55d0aa9ac776a1c847272bf_registry-services-chemical-structure-cas-152342-19-3.avif)
A CAS Registry Number is a numeric identifier that can contain up to 10 digits, divided by hyphens into three parts.
The right-most digit is a check digit used to verify the validity and uniqueness of the entire number.
Improve your digital R&D workflows and ensure compliance when you license CAS REGISTRY data:
Explore our services to obtain CAS Registry Numbers and/or CA Index Names to include in your regulatory submissions, or consult with chemists for expert substance information.