# What Is CoCounsel? Thomson Reuters’ Legal AI Explained

> What is CoCounsel? Thomson Reuters' legal AI assistant, built from its $650M Casetext deal. Where it came from, what the tiers mean and what to ask.

By The Circle Desk | AI in Practice | Published 2026-10-24
Source: https://legaltechcircle.com/insights/what-is-cocounsel-thomson-reuters/

What is CoCounsel? CoCounsel is the generative AI assistant Thomson
Reuters sells to lawyers for research, document review and drafting,
grounded in its Westlaw and Practical Law content. It began as a
product of the legal tech company Casetext, which Thomson Reuters
bought in 2023, and it now comes in several tiers with names that
confuse many buyers.

This explainer covers where CoCounsel came from, what the current
products include according to Thomson Reuters' own pages, and what to
ask before buying. It does not cover what CoCounsel costs in detail;
see our guide to [what legal AI tools
cost](https://legaltechcircle.com/insights/legal-ai-tools-pricing-2026/)
for the reported figures.

## Where CoCounsel Came From

Thomson Reuters [completed its acquisition of
Casetext](https://www.thomsonreuters.com/en/press-releases/2023/august/thomson-reuters-completes-acquisition-of-casetext-inc)
on August 17, 2023, for $650 million in cash. The release described
Casetext as founded in 2013, with customers including more than 10,000
law firms and corporate legal departments, and named CoCounsel as a
key product: "an AI legal assistant powered by GPT-4" for document
review, legal research memos, deposition preparation and contract
analysis.

Three months later, on November 15, 2023, Thomson Reuters [announced
CoCounsel Core](https://www.thomsonreuters.com/en/press-releases/2023/november/thomson-reuters-launches-generative-ai-powered-solutions-to-transform-how-legal-professionals-work)
as the commercial offering of the legacy CoCounsel skills, alongside
AI-Assisted Research on Westlaw Precision. The release said Thomson
Reuters would build on "the AI assistant experience Casetext created
with CoCounsel." That is why some older articles say CoCounsel Core
and newer pages do not.

## What CoCounsel Includes Today

Thomson Reuters' product pages now use two main names for legal
customers. The [CoCounsel Legal
page](https://legal.thomsonreuters.com/en/products/cocounsel-legal)
describes the full assistant: from a single query it handles research,
analysis and drafting, builds a step-by-step plan the user can
inspect, and reasons from Westlaw content, Practical Law guidance
spanning more than 100 jurisdictions and the organization's own
knowledge. It keeps documents, templates and matter history in one
place. It lists connections to iManage, SharePoint, HighQ, Smokeball
and Box, use inside Word, Outlook and Teams, and a CoCounsel Legal MCP
for working within Claude.

CoCounsel Essentials is the narrower tier. The [Westlaw Advantage
page](https://legal.thomsonreuters.com/en/products/westlaw-advantage)
describes it as automating document analysis, review and drafting, and
Thomson Reuters sells it bundled with Westlaw Advantage and with
Practical Law. So a lawyer who says "we have CoCounsel" may mean the
full CoCounsel Legal assistant or an Essentials bundle attached to
Westlaw.

For the wider field, our [Harvey vs. Legora
guide](https://legaltechcircle.com/insights/harvey-vs-legora/) covers
the two largest independent platforms.

## What to Ask Before Buying

Start with the tier. Ask in writing whether the quote is for CoCounsel
Legal or an Essentials bundle, which content sets are included, and
whether Westlaw Advantage is part of the deal.

Ask about terms. Thomson Reuters' [online plans
page](https://sales.legalsolutions.thomsonreuters.com/en-us/products/cocounsel-legal/700/plans-pricing)
sells CoCounsel Legal on one-, two- and three-year terms and says new
features are added to plans as they become available during the
initial term. It does not show prices outside its configurator.

Ask about accuracy and data. The [Stanford study of legal AI
tools](https://dho.stanford.edu/wp-content/uploads/Legal_RAG_Hallucinations.pdf),
which tested Thomson Reuters' Westlaw and Practical Law AI products in
2024, found hallucination rates between 17% and 33% across the legal
tools it tested. Those were earlier products, but the lesson stands:
plan for review. Ask how prompts and documents are retained and
whether they are used for training. Our guide to [ABA Formal Opinion
512](https://legaltechcircle.com/insights/aba-formal-opinion-512-explained/)
explains why those answers matter for confidentiality.

## Common Questions

**Who owns CoCounsel?**

Thomson Reuters. It acquired Casetext, the company that built
CoCounsel, for $650 million in 2023.

**What is CoCounsel Core?**

The name Thomson Reuters gave in November 2023 to the commercial
offering of the original CoCounsel skills. Current pages focus on
CoCounsel Legal and CoCounsel Essentials.

**What is CoCounsel on Westlaw?**

Thomson Reuters sells Westlaw Advantage with CoCounsel Essentials,
which adds AI document analysis, review and drafting to its Westlaw
research product.

**Does Thomson Reuters publish CoCounsel prices?**

Not as a public list. Prices sit inside an online configurator.
Reported figures are covered in our pricing guide.

## The Verdict

**Real.** CoCounsel is a mature product backed by Westlaw and
Practical Law content, and the integrations listed on its page are
broad. The confusion is in the packaging, so get the exact tier,
content and term in writing before comparing it with anything else.

---
Legal Tech Circle (https://legaltechcircle.com/). News and analysis, not legal advice.