Compared · read 2026-11-04
Thomson Reuters has three tools that check the citations in a brief: Quick Check on Westlaw Edge and Precision, Litigation Document Analyzer on Westlaw Advantage, and Brief Builder in CoCounsel Legal. KeyCite sits under all three. Each row below comes from Thomson Reuters' own pages, read on 2026-11-04, next to what proofread.law does and how often it is wrong. All cite checkers compared.
Run Litigation Document Analyzer. It is the broadest of the three: invented cases, quotations, "misrepresentations of law" and negative KeyCite treatment in one report, and a judicial mode for both sides' briefs. Thomson Reuters publishes no error rate for it, so if a filing matters, a second check whose rates are published costs nothing to add: paste the draft here.
Quick Check verifies citations and quotations and shows KeyCite warnings. Its pages make no claim about whether a case supports the sentence that cites it, or about invented cases. That is the gap our deep check covers: it reads the cited passage and says whether it carries your sentence, with the passage shown.
Online Westlaw Advantage pricing starts at $256.75 a month for one circuit. If what you need is "are these cases real, and did I quote them right" before filing, our free tier checks 20 drafts a month without an account, and Solo is $29 a month. You do not get KeyCite; see the next card.
That is KeyCite's job, and Quick Check and Litigation Document Analyzer both show it. We do not answer it for US cases. For Swiss decisions we flag a later leading case that changed or clarified the practice, which is a narrower check.
A citation like 2023 WL 1234567 points into Westlaw's own database. Westlaw resolves it; we cannot, and list it as "cannot verify", never as wrong. In the briefs we measured, about a quarter of citations were Westlaw or Lexis identifiers.
Quick Check and Litigation Document Analyzer both have a mode for an opponent's brief, and a judicial mode that takes up to six documents from one matter. A filed brief is a public record, so it can also go through ours: checking opposing counsel's citations.
| tool | case exists | quotation | says what you cite it for | still good law | error rate published | your document kept | price |
|---|---|---|---|---|---|---|---|
| proofread.law | yes, measured | yes | yes, opt-in deep check | no (Swiss: changes of practice) | yes | no, unless you save it | free for 20 checks a month, then $0.50 a check or $29 a month |
| Quick Check (Westlaw Edge, Precision) | yes | yes | not stated | KeyCite | no | not stated | with Westlaw Edge or Precision; plain Edge not priced online |
| Litigation Document Analyzer (Westlaw Advantage) | yes, "hallucinated cases" | yes | yes, "misrepresentations of law" | KeyCite | no | upload destroyed after the analysis; report deleted within 48 hours | Westlaw Advantage from $256.75 a month, one circuit |
| Brief Builder (CoCounsel Legal) | yes, on briefs it drafts | not stated | yes, "holdings match how they're used" | KeyCite | no | not used for training; retention set per organization | not shown online |
"Not stated": Thomson Reuters' pages do not say. "Yes" for Thomson Reuters is its own claim. Ours is measured: 89% of invented cases caught, 1.2% false flags; at the confidence the report shows, the deep check confirms 55.0% of good citations and marks a wrong passage as support for 4.5% of wrong pairs, which is why it is a review queue and not a verdict. Every number, with its sample and caveats.
If you already pay for Westlaw, Quick Check or Litigation Document Analyzer is the first check to run, because it carries KeyCite and resolves WL citations, and we do neither for US law. What none of the three publishes is how often it misses an invented case or flags a real one. Ours does, and it is free to try without an account, which makes it a cheap second check before filing. If you do not pay for Westlaw, ours covers the existence, quotation and support checks for a fraction of the price, and you check good law separately.
What each page says, quoted, and when we read it. If a page changes, tell us at hello@proofread.law and the row changes.
"Quick Check will verify your citations and quotations." For an opponent's brief it lets you "view KeyCite information for their citations, an analysis of quotations, and to surface relevant cases that oppose your opponent's position." The product page adds "warnings for cited authority, an analysis of quotations, and a table of authorities." It "supports Word documents that are 20MB or less and PDF documents that are 30MB (about 120 pages) or less", and is available inside Drafting Assistant for subscribers to both. No page we read states a retention period or an error rate.
thomsonreuters.com/en-us/help/westlaw-edge/tools/quick-check · legal.thomsonreuters.com/en/products/westlaw-edge/quick-check · read 2026-11-04
"Building on Quick Check, this advanced AI tool reviews entire documents to spot both inaccurate citations and broader misstatements of law." It "Lists citation issues and negative KeyCite treatment" and "Shows potential misrepresentations of law, quotations, and paraphrases that may be out of context"; the product page says it "catches hallucinated cases and weak arguments". The judicial mode takes "up to 6 documents from a single matter." On data: "Following the analysis, Westlaw Advantage destroys the copy you uploaded, and no copy of your work product is retained on Westlaw Advantage servers. The report that is created remains available in History for up to 24 hours and is deleted from Westlaw Advantage servers within 48 hours." Price: "starts at $256.75 per month for single-circuit coverage and $399.75 per month for all states and federal coverage", online for firms with up to 10 attorneys; another Thomson Reuters pricing page says "Starting at $288.60/month". No error rate is published.
legal.thomsonreuters.com/en/products/westlaw-advantage/features · thomsonreuters.com/en-us/help/westlaw-advantage/tools/analyze-briefs-memos · …/access-litigation-document-analyzer · legal.thomsonreuters.com/en/products/westlaw-advantage · Westlaw Advantage plans and pricing · legal.thomsonreuters.com/en/c/westlaw/plans-and-pricing-b · read 2026-11-04
The next generation of CoCounsel Legal, generally available in the US since 2026-08-20, is "Built on Anthropic's Claude Agent SDK". Westlaw Brief Builder drafts briefs "while validating authority along the way. Powered by Westlaw Deep Research, KeyCite, and Practical Law"; a Thomson Reuters post says it "automatically verifies citations, confirming cases exist and holdings match how they're used." Deep Research Verify "checks whether cited Westlaw and Practical Law authority supports specific legal assertions" in Deep Research reports. On data: "Your user content and prompts are not used to train or improve CoCounsel and associated products or LLMs"; retention "is customized… at the organization account level." No price is shown and no error rate is published.
Thomson Reuters press release, 2026-08-20 · legal.thomsonreuters.com blog, 2026-09-25 · thomsonreuters.com/en/cocounsel · read 2026-11-04
"verify whether a case, statute, regulation, or administrative decision is still good law… KeyCite Overruling Risk warns when a point of law in your case has been implicitly undermined."
legal.thomsonreuters.com/en/products/westlaw/keycite · read 2026-11-04
Our rates, samples and engine versions are on measurements; what the register holds and misses is on coverage. Westlaw is a registered trademark of Thomson Reuters; we are not affiliated with it.