CoCounsel is Thomson Reuters' AI legal assistant, originating from Casetext's CoCounsel product (Casetext was acquired by Thomson Reuters in 2023). It handles legal research, contract and document review, deposition preparation, and drafting, and its flagship "Deep Research" feature runs a multi-step agentic research process that returns a cited report.

CoCounsel is most differentiated by its integration with Thomson Reuters' existing legal content: it can be bundled with Westlaw (case law and statutes) and Practical Law (practical guidance and templates), which third-party reviewers note significantly changes the effective price depending on which bundle a firm buys.

As of 2026, Thomson Reuters sells several overlapping configurations — a CoCounsel Core add-on, self-serve CoCounsel Legal plans, and bundles like "Westlaw Advantage with CoCounsel Essentials" — which buyer guides describe as a genuinely complex pricing landscape to compare.

CoCounsel is used across law firms of all sizes as well as in-house legal departments, given Thomson Reuters' existing footprint in both markets.