Is Claude accurate?
Claude had the lowest false-claim rate of 10 chatbots in NewsGuard's August 2025 audit and ranks second on the AA-Omniscience index, though Claude Opus 5.5 still added unsupported content to 9.9% of summaries on the Vectara leaderboard.
Short answer
Claude is one of the most accurate AI assistants in published tests. In NewsGuard's August 2025 audit, Claude repeated false news claims 10% of the time, the lowest of 10 chatbots. Claude Opus 5.5, a model behind Claude, scores 48 on the AA-Omniscience index, second highest. It still makes mistakes.
Results
- Benchmark
- News audit
- Vendor claim
| Test | What was measured | Result | Date | Source |
|---|---|---|---|---|
| NewsGuard AI False Claims Monitor | Rate of repeating provably false news claims | 10% | Source 1News audit | |
| AA-Omniscience | Index score of Claude Opus 5.5, a model behind Claude (right answers minus wrong ones on hard questions) | 48 | Source 2Benchmark | |
| AA-Omniscience paper | Index score of Claude 4.1 Opus at launch | 4.8 | Source 2Benchmark | |
| Vectara Hallucination Leaderboard | Summaries by Claude Opus 5.5, a model behind Claude, that added unsupported content | 9.9% | Source 3Benchmark | |
| Anthropic internal factuality evalVendor's own figure, not independently checked | Accuracy of Claude 3 Opus on hard open-ended questions against Claude 2.1 | Twofold improvement | Source 4Vendor claim |
What these results mean
Claude's strongest result is on false claims. NewsGuard tested 10 leading chatbots on provably false news narratives, and Claude repeated them least often (NewsGuard, 2025-09-04). The audit average was 35%, and Gemini, in second place, was at 16.67%. A low rate here means that when Claude was fed a false news premise, it repeated the falsehood less often than any other chatbot in the audit.
AA-Omniscience asks hard knowledge questions and scores a wrong answer as worse than no answer. That makes it a test of whether a model holds back when it does not know. When the benchmark launched, most models gave more wrong answers than right ones. Claude 4.1 Opus had the highest score in the original paper, 4.8, and was one of only three models above zero (Artificial Analysis). On the live board checked on 2026-10-29, Claude Opus 5.5 scores 48, second to Gemini 4 Carbon (High) at 54.
Anthropic's own figure is older and relative only. It said in March 2024 that Claude 3 Opus doubled accuracy on hard open-ended questions over Claude 2.1, and that incorrect answers fell (Anthropic, 2024-03-04). That is the vendor's claim, on its own question set.
Claude's record suggests it is more willing than most assistants to hold back, but a careful answer is still not a checked one.
Where Claude goes wrong
Summaries
Claude Opus 5.5 added unsupported content to 9.9% of summaries on the Vectara leaderboard, checked as of 2026-10-22. That is mid-pack. Claude Sonnet 4.6 scored 10.6% and Claude Opus 4.7 12.0%.
Not first on every benchmark
On AA-Omniscience, a Gemini model holds the top index score, 54 against Claude Opus 5.5's 48.
Older models differ
The scores above are for named models. A different Claude model, or an older one, will not match them.
Citations still need checking
Like every language model, Claude can give a reference that does not support the claim it is attached to. Treat every reference the same way you would treat one from any assistant: open it and read it.
Claude does well at not repeating known falsehoods. It is less distinctive at staying faithful to a document it summarizes, where several rival models score lower rates.
How it compares
Each table uses one test only.
NewsGuard AI False Claims Monitor (2025-09-04): rate of repeating false news claims
| Chatbot | Result |
|---|---|
| ClaudeThis page | 10% |
 Gemini | 16.67% |
 Microsoft Copilot | 36.67% |
 ChatGPT | 40% |
 Perplexity | 46.67% |
Source: NewsGuard. Claude placed first of 10. See Gemini, the runner-up, and ChatGPT.
Vectara Hallucination Leaderboard (2026-10-22): summaries with unsupported content
| Model | Result |
|---|---|
| Gemini 2.5 Pro (model behind Gemini) | 7.0% |
| GPT-5.5 (model behind ChatGPT) | 9.3% |
| Claude Opus 5.5 (model behind Claude) | 9.9% |
| DeepSeek-R1 (model behind DeepSeek) | 11.3% |
Source: Vectara. On this test Claude sits in the middle. The full table is on AI hallucination rates by model. The overall order of assistants is on the most accurate AI assistants, where Claude is the top pick.
How to check Claude's answers
Ask Claude to say when it is unsure
Its benchmark record suggests it will hold back more readily when invited to.
Open every source it names
Confirm the page exists and says what Claude says it does.
Compare summaries with the original
Pick two or three claims from a summary and find them in the source document. Claude Opus 5.5 added unsupported content to 9.9% of summaries on the Vectara test.
Check numbers, names and dates in the primary record
These are the details most likely to drift.
Re-ask in a new chat
If the answer changes, verify before using either version.
The full routine is on how to fact-check an AI answer. How sources are weighed is on how we score AI accuracy.
Sources
- News audit
- Benchmark
- Benchmark
- Vendor claim
Questions
Is Claude always right?
No. Claude has one of the best records in published tests, but it still makes mistakes. It repeated false news claims 10% of the time in NewsGuard's August 2025 audit, the lowest of 10 chatbots, and Claude Opus 5.5 added unsupported content to 9.9% of summaries on the Vectara leaderboard. Check anything you plan to rely on.
Is Claude reliable for research?
Claude is one of the more reliable assistants for research, as long as you check its sources. Claude Opus 5.5 scores 48 on the AA-Omniscience index, second highest when checked on 2026-10-29, a test that penalizes wrong answers more than no answer. Use it to draft and explore, then cite the original papers and reports.
Does Claude make up sources?
Claude can produce wrong or unsupported references, like any language model. Its summaries added unsupported content 9.9% of the time on the Vectara leaderboard as of 2026-10-22. Open every link and search every paper title before you cite it. Our guide on fake AI citations shows a quick routine for checking references.
Is the paid version of Claude more accurate?
Paid plans give access to larger models, and model choice matters. On the Vectara leaderboard, Claude Opus 5.5 scored 9.9%, Claude Sonnet 4.6 10.6% and Claude Opus 4.7 12.0%. A newer or larger model is not automatically more faithful, so the plan alone does not settle accuracy. Check paid answers the same way.
How do I check a Claude answer?
Tell Claude it may say it does not know. Open each source it names and confirm the page says the same thing. Compare a summary against the original document on two or three key points. Check numbers, names and dates in the primary record. If the answer changes when you ask again in a new chat, verify before using it.
