Bloomberg Law vs Westlaw: how they compare in 2026

The vendor's approach page lists differentiated content as one of four pillars and says the AI does not generate answers on its own but searches a large collection of vetted information. Without the models, 15.5 million court opinions, 200 million dockets, 5 million statutes and regulations, 8,200 practical guidance documents and a newsroom remain, which is what Bloomberg has sold since 2009. Some tools would not survive: BCITE, Docket Key, Points of Law and Litigation Analytics are built with machine learning and do not exist without it. The subscription is flat and all inclusive, and buyers do not buy or meter the AI separately.

Westlaw works as a research service without its generative features. The base Westlaw Edge plan sells case law, statutes, regulations, KeyCite, the Key Number System, headnotes, Litigation Analytics and Quick Check with no generative AI, and Thomson Reuters still licenses it on its own. The models drive the two AI tiers. AI-Assisted Research answers plain language questions with links to authority, and Westlaw Advantage adds Deep Research, which plans and runs multistep research and returns a report, along with Litigation Document Analyzer, Complaint Analyzer, Claims Explorer, AI Jurisdictional Surveys and AI summaries of dockets. Thomson Reuters describes Deep Research as custom trained AI working with Westlaw's own research tools rather than a general chatbot placed over the content.

The vendor names retrieval augmented generation with a proprietary guardrail service, says output is grounded in its own expert or primary content rather than the internet, and says Bloomberg Law Answers cites and links the authorities behind each answer, with one click verification. BCITE, the platform's own citator, reports whether a holding is still good law. The system abstains when no content covers a topic or a question is outside legal scope. No result, test set, sample size or error rate from the described benchmarking by former attorneys is published, although the same page commits to giving customers clear documentation of that benchmarking and validation. The vendor says plainly that AI answers are never fully trustworthy and carry a hallucination risk, and tells customers to check them against primary sources.

Deep Research runs an agentic process over Westlaw and Practical Law content with Westlaw's own research tools. It quotes primary law in the language of the source and links each authority to the full document. Its Verify tab lists cited and further relevant law to check the analysis, and AI Jurisdictional Surveys show KeyCite status beside each source. Litigation Document Analyzer reviews a whole brief for inaccurate citations, misstatements of law and hallucinated cases. Thomson Reuters says Deep Research can occasionally produce inaccuracies. In June 2024 it said internal testing showed AI-Assisted Research accurate about 90 percent of the time, without publishing the test set. The preregistered Stanford RegLab and HAI study (Magesh and others, Journal of Empirical Legal Studies, 2025) ran in May 2024. It found AI-Assisted Research accurate on 42 percent of 202 questions and hallucinating on about a third, nearly twice as often as the other legal tools tested. Thomson Reuters disputed the result, and Deep Research came after the test.

The vendor says it wants its AI to make the job easier, not do it for the user, and describes building one task at a time rather than producing finished work product. Answers carry inline citations with one click verification, abstention is documented with two named triggers, all generative tools are beta tested before release, and customers are told to check answers against primary sources and use their own judgment. Nothing on the approach to AI page, the AI product page or in either agreement describes what happens after an answer proves wrong; no correction or error reporting route is documented, and no confidence threshold or setting is offered. Deep Thinking, which the vendor says automatically plans and runs multistep research before synthesizing results, has no described checkpoint between request and finished answer.

Each AI mode has a stated job and a stated stopping point. AI-Assisted Research answers a question the lawyer asks. Deep Research plans a multistep investigation and runs it without further prompts, shows its approach in step by step research notes, and returns a report with arguments on both sides and links to each authority. Its Enhance tab asks questions to tailor the report, and its Verify tab lists cited and further relevant law. The Deep Research help article sets a categorical limit. Its summary and list of authority should never be used to advise a client, write a brief or motion for a court, or otherwise be relied on without further research. The General Terms add that a licensed professional or similar expert must review AI output before anyone relies on it, uses it or passes it on. Nothing says what Thomson Reuters does once a wrong answer is reported.

The pricing page has three quotes. One names an organization and an outcome: a corporate counsel at Synovos, Inc. says the platform let the team pull state summaries of laws and regulations without calling outside counsel, cutting tens of calls on minor issues and lowering annual legal fees, though with no figure, timeframe or date. The other two are attributed only by role and segment, a small law practice area leader and a large law partner, and both concern the flat pricing rather than outcomes. The home, AI product, approach to AI and pricing pages and the navigation carry no case study with a method, customer count, named law firm or quantified result.

Thomson Reuters says more than 50,000 law firms and legal departments use Westlaw, including 80 percent of the Am Law 100, along with more than 6,000 state government agencies and courts in 94 percent of states. The Department of Health and Human Services has granted Westlaw an Authority to Operate. A Thomson Reuters case study names Justly Prudent, a civil rights litigation firm, and credits CoCounsel and Westlaw AI with five times return on investment and a doubling of litigation capacity, without a method a reader can check. At the Deep Research launch in August 2025, Morgan Lewis's chief AI and knowledge officer was quoted on its reasoning, without figures. Usage of the AI tiers is not reported apart from Westlaw as a whole.

The privacy policy says collected information includes user content, usage, browsing and search history, reading habits and inferences used to profile a user's preferences and behavior. It describes advertising over that material: lookalike or matched audiences on social platforms, sharing a hashed email with ad companies, and sharing for cross context behavioral advertising under California and Virginia law, with opt outs. The policy covers the marketing site and the products together and does not say whether in product search history is excluded. The subscription terms say the site is not meant to hold personal or health information, give no warranty on how it would be held, and reserve a right to audit and monitor use. The documents do commit to notice of subpoenas, Standard Contractual Clauses, an intragroup data protection agreement, and data centers used only for the vendor's operations. No statement on training with customer input, retention period, separation between users or matters, or treatment of privilege or work product is published.

Thomson Reuters' Legal AI Terms of 23 January 2026 govern AI features in its legal products. They bar Thomson Reuters and its third party providers from developing, training or fine tuning any generative or foundation model with user prompts, user content or outputs unless agreed separately in writing. The same terms let Thomson Reuters use prompts and outputs to evaluate safety and effectiveness, with automated safeguards meant to keep sensitive and identifying information out of the samples reviewed. The General Terms let a party disclose the other's confidential information under law, subpoena or court order only with prior notice where legally permitted. The Data Security Addendum keeps each customer's data logically segregated from other customers' data. Attorney client privilege and work product are not addressed by name, and nothing describes separation by matter within a firm.

Both the website terms and the subscription terms say in capitals that none of the services is legal advice, opinion or recommendation, that users needing legal help should consult a competent professional, that users take full responsibility for decisions and conclusions reached through the services, and that no attorney client relationship forms with the vendor or any content supplier. Eligible users are defined: eighteen or older, members of a professional, business or academic community doing professional research, working in a court, government agency, corporation or similar body, or law or business students, with bots excluded. The public approach to AI page addresses competence and supervision, telling customers to check answers against primary sources and use their own judgment, and saying the AI makes the job easier rather than doing it. No bar or ethics guidance is named, including ABA Formal Opinion 512, and no jurisdictional limit on answers is stated.

The General Terms say a licensed professional or similar expert must review AI output before anyone relies on it, uses it or passes it on. The customer alone is responsible for verifying its accuracy, and Thomson Reuters is not liable for decisions based on it. The Deep Research help article says its output should never be used to advise a client or write a brief or motion without further research. It presents the tool as a way to speed research rather than replace it. Westlaw is sold to law firms, legal departments, courts, government agencies and law schools, and the online plans are for law firms. Nothing addresses a lawyer's competence duties or names a jurisdiction's ethics rules.

The approach to AI page, last modified 18 June 2026, sets out four pillars and gives the accuracy pillar substance: retrieval augmented generation plus a proprietary guardrail service, output grounded in vetted first party or primary material rather than the open internet, beta testing of every generative tool before release, and accuracy evaluation by former attorneys from development through internal, beta and customer testing and over the product's life, with continuous tuning against model drift. It commits to documenting where and when products use generative AI, the sources used, and the benchmarking and validation process. No accountable owner is named, and no test result is published against that benchmarking commitment. Nothing addresses bias or uneven output across matter types, jurisdictions or populations, and the platform profiles named judges, attorneys and firms. Its trust center lists a document titled AI Frequently Asked Questions.

Westlaw Edge, Precision and Advantage sit inside Thomson Reuters' ISO/IEC 42001:2023 certificate for its AI management system, issued by MSECB, held since March 2025 and valid to March 2028, and the certificate is published on the trust center. The Data and AI Governance and Security Program whitepaper of March 2025 makes the Responsible AI and Data Trust team responsible for AI governance and sends sensitive data uses to a Model Ethics Committee. Every business model must be registered in a central compliance hub and go through a data impact assessment that sets ethics controls such as human oversight and fairness, a model risk assessment, documented design and testing, monitoring and decommissioning. Attorney editors test and validate Westlaw's AI. No test results, bias findings or differences in performance across practice areas or jurisdictions are published.

The privacy policy, updated 9 July 2026, says personal information is held on secure servers under administrative, technical, personnel and physical measures, and sets retention by criteria rather than a number: the time needed for the purpose, whether the user has stopped using the products, any legal proceedings, and legal or regulatory requirements. It describes a personal data governance program, a data map of flows within the vendor's systems and to third parties, ongoing testing of safeguards, company wide privacy training, and data centers used only for the vendor's own products and operations with monitored access. Standard Contractual Clauses and an intragroup data protection agreement cover transfers, with further processing terms available where the vendor acts as processor. The trust center adds data erasure, backups, access monitoring, least privilege and logging, and a full responsible disclosure policy. No retention period, named subprocessor or breach notification commitment is published.

The Data Security Addendum, last modified 26 October 2026, encrypts customer data with 256 bit AES in transit and at rest. It limits access to authorized personnel with multifactor authentication, keeps each customer's data logically segregated, and commits to notice of a security breach within 72 hours. It offers a summary of penetration test results on written request and destroys customer data at the end of the service on request. The General Terms delete production data within 90 days after termination on written request, and the Data Processing Addendum dated 15 October 2026 deletes personal data on request. Thomson Reuters names the outside AI providers behind its generative features as Amazon Web Services, Anthropic, Google, Microsoft and OpenAI. No retention period is stated for prompts, uploaded documents or research history during a subscription, and the Westlaw data retention overview for Litigation Document Analyzer sits behind a Whistic account.

The subscription terms, updated November 2025, cap total liability at 500 dollars whatever the form of action, disclaim all warranties including merchantability, fitness for purpose and noninfringement, provide the services as is and as available, and do not guarantee accuracy, correctness, completeness or timeliness. One exclusion covers research itself: no liability for any inability or failure to perform legal or other research, or to do it properly or completely, even with the vendor's help. Users are solely responsible for the accuracy and adequacy of data used and the output, and any action must be brought within one year. Virginia law governs, with exclusive jurisdiction in Arlington County. The only exception to the cap is death or personal injury from negligence where the law forbids limiting it. Nothing runs to the customer: no indemnity, output warranty or AI specific term. Its trust center lists a certificate of liability.

Thomson Reuters' General Terms for the United States (version 6.0, 1 September 2026) cap each party's liability in a calendar year at the fees paid for the affected service over the prior twelve months. That cap doubles for breaches of confidentiality, data protection or security, and indirect and consequential loss is excluded. Thomson Reuters defends and indemnifies the customer against third party claims that use of the service infringes intellectual property, and that indemnity sits outside the cap. The service warranty promises conformity with the documentation, with repair, modification or replacement as the remedy. For AI output, the terms disclaim liability for its accuracy, legality or reliability and for decisions based on it.

Two integrations are described. The vendor's newsroom describes Bloomberg Law Contract Solutions as integrating with Microsoft Word alongside a central contract repository, and the subscription terms cover users reaching Bloomberg Law through the Bloomberg Professional service, the Terminal, whose own agreement then applies. The navigation, the AI product page, the approach to AI page and the footer show no integrations page, developer or API documentation, or named connection to document management, matter management, ebilling or court filing. Dashboard Legal is a project management and collaboration product, not a bridge into a firm's systems.

Westlaw's product and plan pages name no document management, practice management or Microsoft Word integration. The AI tools work on what a lawyer types or uploads: Litigation Document Analyzer, Complaint Analyzer and Quick Check take an uploaded brief or complaint. Deep Research also runs inside CoCounsel Legal, the separate Thomson Reuters assistant, which connects to iManage, NetDocuments and SharePoint. Thomson Reuters lists terms for a document management system integration among its legal products without saying what it moves or how a firm sets it up.

The privacy policy's intragroup data protection statement says the vendor's data centers serve only its own products, services and operations, with secure, monitored access. Transfers are acknowledged: personal information may be processed in various countries with differing protection, including the United States, under Standard Contractual Clauses and an intragroup agreement naming exporters and importers. Nothing published offers a region or residency choice, describes the platform's tenancy, separates processing from storage, or says where generative features run. Its trust center lists a data center item. These statements sit in a personal data annex, not in product or security material.

Westlaw is a hosted service, and the Data Security Addendum keeps each customer's production data logically segregated from other customers' data. The Department of Health and Human Services has granted Westlaw an Authority to Operate, and Thomson Reuters says Westlaw is in the final stage of FedRAMP authorization. Separate security summaries cover the American, UK, Canadian, Australian and New Zealand editions. No hosting provider, region or residency commitment is published for the American service, and nothing separates where AI processing runs from where data is stored.

Every page footer links to the trust center under Trust and Security, with a product identifier in the address. It is a SafeBase portal reachable without a sales call, listing a penetration test report, security whitepaper, SOC 1 and SOC 2, a SIG Lite self assessment, a certificate of liability, a business continuity management document and an AI FAQ, along with control areas for product, access, application and network security, business continuity and training, and a full responsible disclosure policy. SOC 1 and SOC 2 are named without a Type, and no auditor, coverage period, report date or scope is published. Documents are split into public and private, with an access request whose terms are not stated.

The Westlaw security profile on Whistic, linked from the Thomson Reuters trust center, lists a Westlaw SOC 2 Type 2 report dated October 2025 and a bridge letter of November 2026, alongside a SIG Lite questionnaire, security summaries by country and an AI security FAQ. Downloading them needs a Whistic account under a Thomson Reuters confidentiality agreement, and the profile does not say the release is immediate. The ISO/IEC 42001:2023 certificate, which names Westlaw Edge, Precision and Advantage, is published openly. The Department of Health and Human Services has granted Westlaw an Authority to Operate, and FedRAMP authorization is in its final stage. The Data Security Addendum lets a customer review an executive summary of ISO 27001 or SOC 2 results on request. The SOC auditor and the report's scope are not stated publicly.

The vendor publishes retrieval augmented generation as the framework, a proprietary guardrail service over it, generation grounded in its own expert and primary content rather than the internet, and large language models trained on that content. It also cites machine learning, natural language processing, information retrieval, recommendation systems and large language models, and says Bloomberg Industry Group employs hundreds of AI researchers and engineers who publish research each year. Nothing published says whether a third party foundation model sits underneath: the phrase used is our large language models, without saying they are built in house. No model name, version, inference location or subprocessor is given, and there is no commitment to notify customers of model or training changes. Its trust center lists a subprocessors item and an AI FAQ.

Thomson Reuters names the outside AI providers whose terms apply to its generative AI products: Amazon Web Services, Anthropic, Google, Microsoft and OpenAI. Deep Research is described as custom trained AI combined with Westlaw's research tools. Nothing maps a provider or model to AI-Assisted Research, Deep Research or the litigation tools, says where inference runs, or commits to notice before the providers change. Thomson Reuters announced its own legal model, Thomson, in August 2026 for CoCounsel Legal's tabular analysis, and nothing says it runs in Westlaw.

The charging model is stated: one platform, one flat all inclusive price, with unlimited access rather than per search or per document charges. A customer quote on its pricing page says occasional use of a tool costs nothing extra, and the request form names two products, Bloomberg Law Research and Bloomberg Law Dashboard Legal. The pricing page, getting started entry, AI product page and navigation give no figure, unit of charge, tier names, feature splits, term length or implementation charge. Every route to a number is a form, and the Request Pricing page is a lead capture form. Its firm size ranges, from solo to fifty or more practitioners, suggest price varies with headcount, but they are form fields, not a published price structure.

Thomson Reuters prices Westlaw online for new customers at law firms of up to 10 attorneys, by number of attorneys, jurisdiction and term. Westlaw Edge with AI-Assisted Research starts at $155.35 a month for single circuit coverage and $266.50 for all states and federal coverage, both on a three year term. Westlaw Advantage starts at $256.75 a month for single circuit coverage and $399.75 for all states and federal. Two year terms take 12 percent off and three year terms 18 percent, and plans include new features released during the initial term. Westlaw Edge without AI is sold online with no starting price stated. Firms with more than 10 attorneys and existing customers are quoted by sales, and documents outside a plan are charged at rates in Westlaw's subscriber pricing guide.

Four buyer groups have solution pages: law firms, in house counsel, government and law schools, and the government page promises unlimited access to state and federal coverage. The vendor's forms list law firms, tax and accounting firms, corporations, nonprofits and associations, consulting firms, education institutions and government, with firm size ranges from solo to fifty or more practitioners. Content is quantified precisely: more than 15.5 million court opinions growing by about 50,000 a month, about 200 million dockets with more than 21 million pleadings, more than 5 million statutes and regulations, 75 million EDGAR filings and more than 8,200 practical guidance documents, with Docket Key covering over 200 motion and brief types across all federal district courts and Chart Builders comparing rules state by state. Nothing says where coverage stops: no supported practice area list, no coverage table by jurisdiction, no statement of state court depth, and no acknowledged gap.

Westlaw serves law firms of every size, corporate legal departments, courts, prosecutors, public defenders, city attorneys, law enforcement, other government agencies and law schools. Thomson Reuters publishes practice area pages for business and commercial law, civil litigation, criminal defense, family law, labor and employment, mergers and acquisitions and personal injury. Content covers state and federal case law, statutes, regulations, court rules, administrative materials, dockets, briefs and secondary sources such as Wright & Miller and Corpus Juris Secundum. The plans set the limits. Westlaw Edge carries no generative AI, AI-Assisted Research and AI Jurisdictional Surveys come with Edge with AI-Assisted Research, and Deep Research, Litigation Document Analyzer, Complaint Analyzer and Claims Explorer come only with Advantage. A single circuit plan covers state and federal primary law for one circuit. Online buying stops at 10 attorneys, and separate editions serve the UK, Canada, Australia and New Zealand.