The West Key Number System is a master classification system of U.S. law.

Westlaw assigns a topic and key number to each legal issue within a case. The Key Number system makes it easier to find other cases addressing the same legal topic in any jurisdiction.

Browse Key Number System topics alphabetically, or conduct a title search:

The Key Number system works in conjunction with Headnotes. Each headnote is assigned one or more topics and Key Numbers. Headnotes are also numbered so you can click on the number to go to the spot in the document where the legal issue is discussed: