CoCounsel
CoCounsel is Thomson Reuters' AI legal assistant, built on GPT-4 with deep integration into the Westlaw legal research database. It answers complex legal questions with cited sources drawn from verified case law and statutes, performs contract review and redlining, and can process large document sets for due diligence. Unlike general-purpose AI tools, every answer is grounded in Thomson Reuters' legal content, making it suitable for use in professional legal practice. It is used by Am Law 100 firms and corporate legal departments looking to reduce time on research, review, and drafting without sacrificing accuracy.
Pros - Built on Thomson Reuters' Westlaw, so legal research answers cite real, verified case law and statutes
- Handles multi-step legal tasks end-to-end — not just Q&A — including drafting and document review
- Trusted by Am Law 100 firms and large corporate legal teams with enterprise-grade security and audit trails
Cons - Priced at the enterprise tier — not accessible to solo practitioners or small firms without significant budget
- Requires attorney oversight; AI outputs must be verified before use in filings or client advice
- Tightly integrated into the Thomson Reuters ecosystem, limiting flexibility for firms using competing research platforms
Best for: Large law firms running high-volume contract review and due diligence on M&A transactions, Corporate legal teams that need to research regulatory questions and draft memos with cited authority quickly, Litigation departments preparing for depositions or reviewing discovery documents across thousands of files
Key features: Legal research with cited, verifiable answers drawn from Westlaw's full database, Contract review and redlining with AI-identified risks and suggested clause changes, Deposition preparation by extracting key testimony and inconsistencies from transcripts, Document review and due diligence across large document sets with custom issue tagging, Draft legal memos, summaries, and correspondence grounded in cited legal authority
Harvey AI
Harvey AI is an enterprise AI platform for law firms and legal teams, built on custom large language models trained specifically on legal data and case law. It handles the most time-intensive legal work — contract analysis, M&A due diligence, litigation research, and regulatory review — at a scale and speed that is not possible with manual attorney effort alone. Harvey is used by top Am Law 100 firms including A&O Shearman and by PwC Legal, where it supports both client-facing work and internal legal operations. Unlike general-purpose AI tools, Harvey's models can be fine-tuned on a firm's own precedent documents and preferred drafting positions.
Pros - Purpose-built for law with custom large language models trained on legal data, not general-purpose AI adapted for legal use
- Trusted by leading Am Law 100 firms including A&O Shearman and PwC Legal, establishing it as an institutional-grade tool
- Handles the full range of legal practice areas — transactional, litigation, and regulatory — from a single platform
Cons - Exclusively enterprise-priced and sold through direct sales, making it inaccessible to small firms and solo practitioners
- Requires attorney supervision for all outputs — not a replace-the-lawyer tool, which means time savings are bounded
- Deep customization to a firm's own precedents and style guides requires a significant onboarding investment
Best for: Am Law 100 and international law firms handling high-volume M&A due diligence and contract review mandates, Big Four and consulting firm legal departments that need AI legal research and regulatory analysis at scale, Large corporate legal teams running structured review processes across thousands of documents in a matter
Key features: Contract analysis that identifies key terms, obligations, risks, and deviations from standard positions, M&A due diligence automation across large document sets with custom issue spotting and extraction, Litigation research that synthesizes relevant case law and produces structured legal memos, Regulatory analysis for compliance teams tracking changes across jurisdictions, Custom LLMs trained on a firm's own precedent documents and work product for matter-specific output