Last reviewed on October 3, 2026.
Many lawyers now use a general-purpose AI assistant alongside, or instead of, legal-specific tools. The three most common are OpenAI's ChatGPT, Anthropic's Claude and Microsoft Copilot (especially Microsoft 365 Copilot inside Word and Outlook). All three change quickly, so treat this as a framework rather than a feature list, and check each vendor's current terms.
What they are good at in legal work
- First drafts of letters, emails, clauses and internal memos from your own notes.
- Summarising long documents you upload (contracts, transcripts, correspondence).
- Rewriting for tone or plain language, and producing checklists or issue lists.
- Brainstorming arguments or questions to ask, which you then research properly.
Where they should not be trusted
- Case law and citations. General assistants can produce convincing but non-existent cases. In Mata v. Avianca (S.D.N.Y. 2023) lawyers were sanctioned for filing fabricated citations generated by ChatGPT, and similar incidents have followed in other courts. Verify every authority in a proper research tool with a citator.
- Current law. Unless the tool is searching and citing reliable sources, it may not reflect recent changes.
- Final advice. Output is a draft for a lawyer to check, not advice.
How the three differ
| ChatGPT | Claude | Microsoft 365 Copilot | |
|---|---|---|---|
| Where you use it | Web and desktop/mobile apps; integrations | Web and desktop/mobile apps; integrations | Inside Word, Outlook, Teams and other Microsoft 365 apps |
| Strength | Broad feature set (files, web search, custom GPTs) | Long-document reading and careful drafting | Works on your organisation's own Microsoft 365 content |
| Business plans | Business/Enterprise tiers with admin controls | Team/Enterprise tiers with admin controls | Licensed per user on top of Microsoft 365 |
| Main caution | Consumer settings may allow training on chats | Consumer settings may allow training on chats | Only as well-governed as your M365 permissions |
Model quality changes several times a year, so we do not rank one assistant above the others. For a specific task, test all three on the same anonymised sample.
Confidentiality: the deciding factor
The ABA's Formal Opinion 512 (July 2024) says lawyers using generative AI must consider competence, confidentiality, client communication, supervision and reasonable fees. In practice:
- Do not paste client confidential information into a consumer account. Consumer plans of these services may use conversations to improve models unless you change the settings.
- Use a business or enterprise plan whose terms say your data is not used for training, with retention controls and an agreement your firm has reviewed.
- For Microsoft 365 Copilot, tidy up SharePoint and Teams permissions first: Copilot can surface any document a user already has access to.
- Record which tool was used for what, and follow your firm's AI use policy.
When a legal-specific tool is the better choice
For legal research, use a platform with a citator and verified sources, such as Westlaw with CoCounsel, Lexis+ AI or vLex Vincent AI. Legal platforms such as Harvey (see our Harvey AI article) add legal workflows, firm-level controls and sometimes legal content on top of general models. For contract review at volume, a CLM tool with playbooks is usually more reliable than ad-hoc chat.
A simple decision rule
- Is there client confidential information? If yes, only use an approved business/enterprise tool.
- Does the output depend on accurate citations? If yes, use a legal research platform and verify.
- Is it drafting or summarising your own material? A general assistant on an approved plan is usually fine, with lawyer review.
Related: ChatGPT in legal practice and the legal AI ethics framework.
Frequently asked questions
Which is better for lawyers: ChatGPT, Claude or Copilot?
There is no single winner. ChatGPT and Claude are strong general assistants for drafting and summarising; Microsoft 365 Copilot is most useful when your work lives in Word, Outlook and Teams. The deciding factors are usually confidentiality terms and your firm's existing software.
Can lawyers use ChatGPT for legal research?
Only with great care. General assistants can invent case citations. Use them for ideas, then verify every authority in a legal research platform with a citator.
Is it safe to put client information into ChatGPT or Claude?
Not in a consumer account. Use a business or enterprise plan with terms your firm has reviewed that exclude your data from model training, and follow your AI use policy and professional rules.