Did the AI change your numbers?
Number Check compares the numbers in an AI answer with the numbers in your original text. It marks every number the AI wrote that is not in the original and suggests what it may have been changed from. It runs entirely in your browser: nothing is uploaded or stored.
Example loaded below: the AI summary turned 420 into 240, 9% into 19% and $6,000 into $600. Press Clear to use your own text.
How do I check AI output for hallucinations?
- Keep the original next to the AI answer. A hallucination is easiest to spot as something the source doesn't contain.
- Check the numbers first with Number Check. Dates, amounts and percentages are where a small change does the most damage. In our weekly AI accuracy test, dropped and changed numbers are among the most common mistakes.
- Check names and quotes by searching the original for them. An AI can produce a quote that sounds right but never appears in the source.
- Ask the AI what the source does not say. In our trap questions, a good answer points out missing information instead of filling the gap.
What Number Check catches, and what it doesn't
Catches: numbers written with digits, including amounts with $, € or £, percentages, years and decimals. Numbers that look like a changed version of an original number (an extra digit, a missing zero, swapped digits) get a suggestion.
Doesn't catch yet: numbers written as words (three, six-month), units that changed while the number stayed the same, and wrong facts that contain no numbers. A number in the original that the AI didn't use is listed for you to look at, not counted as an error: a summary is allowed to leave things out.
Is my text uploaded anywhere?
No. The comparison is a small script that runs on this page in your browser. The text you paste is not sent to a server, not stored, and not used to train any model, so it is safe to use with internal documents.