How to Fact-Check ChatGPT Answers

Choose the claims worth checking first

Read the answer once and underline names, dates, numbers, quotations, causes, product capabilities, prices, rules, and recommendations that depend on a factual premise. Split a sentence when its parts could earn different verdicts. A correct launch date, for example, does not rescue an incorrect landing date in the same sentence.

Check first anything that affects safety, money, rights, eligibility, a deadline, someone's reputation, or an action you cannot easily undo. For a casual background detail, one suitable source may be enough. A medical instruction, legal duty, or financial decision needs current authoritative evidence and, where appropriate, a qualified professional. If you cannot make that check, leave the claim out of the decision.

Run four checks on each important claim

1. Find the original. Open the cited URL. Check the publisher and the page itself; a plausible citation title, search snippet, or ChatGPT preview is not the source. If the answer gives no citation, search for the original record rather than asking the model to endorse its own statement.
2. Locate direct support. Find the section, table, page, or timestamp that addresses the precise claim. A page about the same subject may support only part of a sentence. Read the surrounding text for conditions and exclusions.
3. Check the time and scope. Record when the source was published or updated and when you opened it. For changing facts, verify the applicable plan, location, version, or date. An undated page cannot by itself establish that a price or policy is current.
4. Challenge the result. Recalculate figures from their inputs. For a consequential or disputed claim, look for another source that adds independent evidence; several articles repeating one announcement are one evidence chain. If the original source is authoritative for its own product or rule, say what it establishes and what it cannot establish.

Keep the source open while you write the verdict. The passage may support the date but not the event, or the number but not the explanation beside it.

Check a real ChatGPT Search answer

On September 26, 2026, we used ChatGPT web with Web search selected and the model selector set to “Instant.” The prompt was: “When did NASA’s Perseverance rover launch and land, and how many days was its trip to Mars? Please cite NASA sources.” The answer gave July 30, 2020 for launch, February 18, 2021 for landing, and 203 days of travel. It also supplied a launch time, rocket, landing site, touchdown confirmation time, and distance. Those extra details need checking even though the question did not ask for them.

The answer to the user's actual question survives the check. The visible first link in the landing citation group was a pre-landing plan; the second link supplied the outcome. The time-of-confirmation wording also went beyond the later announcement. If you only needed the dates and duration, a checked short answer is: “Perseverance launched on July 30, 2020 and landed on February 18, 2021, after a 203-day journey, according to NASA's mission record and touchdown announcement.”

Worked check: a current ChatGPT Search claim

Here is an editorial practice sentence about a changing product feature: “ChatGPT Search is available only on paid plans, and every answer includes citations that prove it is correct.” It contains three claims: who can use Search, whether every answer has citations, and whether a citation proves accuracy.

Open the official Searching the web with ChatGPT page. Its “Availability” section lists ChatGPT Free alongside paid plans and says searches are subject to plan usage limits. Its “Review sources and results” section says responses using web search may include citations and warns that results and citations can be incomplete, outdated, or incorrect. The three claims are contradicted by the provider's current guidance: Free access exists, citations are not promised on every answer, and a citation does not certify the text beside it. The page showed a relative update label when checked on September 26, 2026; record the check date rather than inventing a precise publication date from “last month.”

Correction: ChatGPT Search is available on Free and paid plans, subject to plan limits. Search responses may include citations. Open the relevant links before repeating a factual claim, and recheck the provider page when plan access matters to a current decision.

Split a mixed sentence into separate verdicts

Change one clause of the real answer above and you get this editorial exercise: “NASA's Perseverance rover landed on Mars in 2020, 203 days after its July 30, 2020 launch.” The 203-day interval remains right, while the landing year becomes wrong. Check the clauses separately.

The NASA mission page's “Launch / Landing” field gives July 30, 2020 / February 18, 2021. The touchdown announcement confirms the 2021 landing and says the trip took 203 days. Both pages come from NASA, so count them as one first-party evidence chain. The dates also give 203 elapsed calendar days when subtracted independently.

The JPL press kit listed the landing date before it happened. Its date is useful for understanding the plan; the touchdown announcement is the record of what happened. This distinction also mattered in the real answer's citation audit.

Verdict: partly supported. Keep the launch date and day count; change the landing year to 2021. The corrected sentence is: “Perseverance launched on July 30, 2020 and landed on Mars on February 18, 2021, 203 elapsed calendar days later.”

Handle missing, stale, and conflicting evidence

Use ChatGPT to organize the check

ChatGPT can extract claims and compare passages you provide. It cannot make a source authentic by repeating it. Keep source discovery and verdicts separate: first collect the original pages, then paste the relevant excerpts with their URLs and dates into a comparison request.

Split the answer below into independently checkable claims. For each claim, give its type, why an error would matter, and the kind of original source to inspect. Do not decide whether a claim is true or invent citations.

[Paste the answer]

Compare the claim only with the source passages I provide. For each passage, say whether it directly supports, partly supports, contradicts, or does not address the claim. Name the exact mismatch. Do not use outside facts or treat two pages repeating one announcement as independent confirmation.

Claim: [exact claim]
Source A: [URL, publication or update date, section, exact excerpt]
Source B: [URL, publication or update date, section, exact excerpt]

Open the original pages again after the comparison. If ChatGPT misreads a table, drops a condition, or supplies a passage you did not paste, correct the record yourself.

Record a verdict and revise the answer

Use supported only when suitable evidence establishes the full claim as worded. Use partly supported when a date, scope, or clause must change; contradicted when suitable evidence conflicts with it; and unverified when you lack adequate evidence. Label an opinion or inference as such instead of presenting it as a sourced fact. These are evidence verdicts, not scores of how confident the prose sounds.

Keep the correction next to the original claim. For the live Perseverance answer, record the exact prompt, the answer's wording, the JPL planning page, the later NASA announcement, the September 26, 2026 check date, and the narrower wording about when confirmation was announced. A list of links without passages or a revision decision will not let a second reader repeat the check.