CourtListener Citation Lookup
Free Law Project's nonprofit case-law site. Its free Citation Lookup Tool and its Citation Lookup API, built as a guardrail against hallucinated citations, check whether a cited case exists.
Visit CourtListener Citation Lookup ↗
AI features
- Web Citation Lookup Tool: type in one case citation and go straight to the opinion, free
- Citation Lookup API: send up to 64,000 characters (about 50 pages) and it extracts every case citation and flags ones not found, with invalid reporters or ambiguous matches
- Checks up to 250 citations per request against a database of more than 18 million citations, using the Eyecite parser built with Harvard Library Innovation Lab
- An MCP server lets AI assistants query CourtListener data directly
Pricing
The website and the one-at-a-time Citation Lookup Tool are free. The API needs an account token; Free Law Project says its APIs are available as a membership benefit and through commercial agreements.
Best for
A free first pass to confirm every case citation in a draft actually exists.
Watch out for
It only tells you whether a case is in CourtListener's database. It doesn't check that the case says what you cite it for, doesn't tell you whether it's still good law (there's no citator), and doesn't look up statutes, law journals, id. or supra citations. A 'not found' result can mean a gap in coverage, so confirm in a full research database.
Playbooks that use CourtListener Citation Lookup
Sources
- CourtListener: Citation Lookup Tool
- CourtListener: Citation Lookup and Verification API documentation
- Free Law Project: Combat hallucinations with our citation lookup API (April 2024)
- CourtListener: Legal APIs and data (pricing and access)
Last verified 2026-10-19.