Does ChatGPT give the same answer to everyone? No, and here is why.
No. ChatGPT writes every answer fresh, so two people asking the same question, or one person asking twice, can get different answers. OpenAI documents that its models are non-deterministic by default, and the product adds memory, web search and location on top. For a brand, that means one screenshot proves very little: whether ChatGPT recommends you is a rate, and it has to be measured across many answers.
Why does ChatGPT give different answers to the same question?
Because it chooses each word by sampling from probabilities rather than looking up a stored reply. OpenAI's API documentation says chat completions are non-deterministic by default, which means model outputs may differ from request to request. Even developers who fix every setting are warned that OpenAI's own changes to model configurations can affect the result.
In a short factual answer the wording shifts and the substance holds. In a list of recommended products, the same sampling decides which names make the cut and in what order, so the brands in the list can change from one ask to the next.
Does ChatGPT personalise its answers for each user?
It can. ChatGPT's memory lets it remember details from earlier conversations and use them in later answers, and users can add custom instructions about themselves. Someone who has told ChatGPT their budget, location or favourite brands may get a shortlist shaped by that.
Users can turn memory off, and a temporary chat does not use it. A logged-out visitor has no history at all. Those are the closest things to a neutral answer, and even they are still sampled.
Does location change what ChatGPT answers?
When ChatGPT searches the web, yes, it can. The pages a search returns depend on where it runs, and OpenAI's own web search tool for developers takes an approximate user location, country, city, region and time zone, to refine results by geography. A buyer in London and one in Chicago asking for "the best payroll software" may each get local options, and both answers are right for where they asked. That is why, on a Proofsource Custom plan, each question can be asked from the market it targets and each market is read on its own.
Does the answer change when ChatGPT's model changes?
Yes. OpenAI replaces the models behind ChatGPT over time, and each model has learned from different text and weighs sources differently. An answer from last month may have come from a different model than today's. That is why a careful tracker records the model version behind every answer, as Proofsource does.
How much do AI answers actually vary from day to day?
More than most brand owners assume. In Proofsource's own sampling, 9% to 27% of the brands named in an engine's answers turn over from one day to the next, depending on the engine: Perplexity moved most and Claude least. That is with nobody publishing anything.
Small samples hide this. In the public Tesla example, ChatGPT named Tesla in 16 of 25 buyer answers, which is 64%, but the 95% Wilson interval runs from about 45% to 80%. Another 25 answers on another day could land anywhere in that range without anything having changed.
Three reasons two answers differ
Each answer is a draw
The model picks words by probability, so the same prompt can produce a different list.
Memory and location
Saved memories, custom instructions and where the search runs can all shape the result.
The model changes
A new model behind ChatGPT can name different brands for the same question.
How do you measure a ChatGPT answer that changes every time?
Ask the same questions many times, from sessions with no personal history, and report a rate with an interval instead of a single result. That is what Proofsource does. It asks your buyer questions on ChatGPT, Perplexity, Claude and Google AI Overviews, keeps every answer, records which brands were named and which model wrote each one, and puts a 95% Wilson interval on every rate.
A change is flagged only when it is bigger than the interval, so a quiet Tuesday is not reported as a crisis. The method is set out on the methodology page, and the trial is 2 days of full AI visibility, today and tomorrow.
What does this mean if you are checking your own brand in ChatGPT?
- Your own chat is the least reliable test. Your memory and history may nudge ChatGPT towards your brand.
- Use a temporary chat or a logged-out window for a cleaner look, and ask the question the way a buyer would, without your brand name in it.
- Ask more than once, and on more than one day, before drawing a conclusion.
- Check the other engines. Perplexity, Claude and Google AI Overviews can disagree with ChatGPT on the same question.
What people ask about ChatGPT's answers
If ChatGPT names my brand when I ask, will my customers see the same answer?
Not necessarily. Your own chats may carry memory or instructions that favour you, and every answer is sampled afresh. Check from a temporary chat or a logged-out window, ask several times, and treat the result as a rate rather than a yes or no.
Does ChatGPT give the same answers to everyone in the same country?
No. Location narrows what a web search returns, but sampling, memory and the model version still vary the answer between two people in the same city.
Does a temporary chat give a neutral answer?
It removes memory from the picture, which makes it a fairer check than your normal chat. It does not remove sampling, so two temporary chats can still differ.
Do Perplexity, Claude and Google AI Overviews vary too?
Yes. In Proofsource's sampling, between 9% and 27% of named brands turn over day to day depending on the engine, with Perplexity moving most and Claude least. Google AI Overviews also appear for some queries and not others.
- OpenAI API docs: advanced usage (reproducible outputs) developers.openai.com/api/docs/guides/advanced-usage
- OpenAI Help Center: Memory FAQ help.openai.com/en/articles/8590148-memory-faq
- OpenAI API docs: web search (user location) developers.openai.com/api/docs/guides/tools-web-search
Sources read on .
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