Markdown edition

# ChatGPT ads can use customer lists and conversation context

> 404 Media tested ads in ChatGPT. OpenAI's documentation explains how customer lists and conversation context can influence delivery, while internal hashing of raw identifiers remains unclear.

By BIG CHANGE Editorial

Published: 2026-10-15T20:21:17.536Z
Updated: 2026-10-15T20:21:17.536Z
Canonical: https://bigchange.ai/blog/chatgpt-ads-customer-lists-conversation-hints

![Conceptual charcoal illustration of a closed card-file box beside an unbranded phone with two empty conversation bubbles and a separate blank orange ad card.](https://bigchange.ai/api/media/file/chatgpt-ad-signals-concept-hero-v1.png)
AI-generated conceptual illustration by BIG CHANGE; no real user data, OpenAI interface or tested ad result is shown.

Advertisers can upload customer identifiers to build audiences for ChatGPT ads, while the subject of a user's current conversation can help determine which ads appear. [404 Media reported on October 15](https://www.404media.co/how-chatgpt-targets-ads-to-you-based-on-your-prompts-phone-number-and-email/) that it ran two ads to examine the system. OpenAI's own [advertiser documentation](https://help.openai.com/en/articles/20001346-set-up-custom-audiences-for-your-campaign) confirms the list-based controls, including uploads of email addresses, phone numbers and Android advertising IDs.

The reporting brings two different forms of targeting into view. An advertiser's list can affect whether a campaign is eligible to reach a user or how much it bids for that user. A separate signal is what the user is discussing in ChatGPT. OpenAI says that current conversation context can inform ad selection even when the user turns off ad personalization.

## The big change

- **What changed:** 404 Media tested ChatGPT advertising and documented an advertiser experience that includes conversation hints and customer-list targeting. OpenAI's published instructions describe the controls available to advertisers.
- **Why it matters:** An ad below a ChatGPT reply can be influenced by the current discussion and, where the audience feature is available, by an advertiser's existing list of people. A user cannot infer the precise reason for a single placement from its appearance alone.
- **What remains open:** OpenAI accepts both raw and SHA-256-hashed email addresses and phone numbers. Its public instructions do not say whether raw identifiers are hashed internally before matching, and 404 Media reported that the company did not answer that question.

## What the reporter tested

404 Media's Joseph Cox wrote that the outlet ran two ads in ChatGPT. The ads directed readers to its reporting on human review of some ChatGPT conversations. For one campaign, the outlet supplied a hint about conversations concerning privacy and technology. The report includes a screenshot of one of its ads in ChatGPT. Those are 404 Media's observations; BIG CHANGE did not create an ad or independently test delivery.

OpenAI's [context-hint guidance](https://help.openai.com/en/articles/20001521-write-context-hints-for-chatgpt-ads) says advertisers add descriptions of a product and the situations where it may be useful at the ad-group level. The hints guide relevance. They are not exact keywords or instructions that force an ad to appear beside a particular prompt. OpenAI says ad selection can also consider the current conversation, the ad and its landing page, bids and, when enabled, signals from a user's broader ChatGPT experience. The public documentation does not expose the weight of each signal for a particular ad.

## How customer lists affect delivery

OpenAI's [custom-audience instructions](https://help.openai.com/en/articles/20001346-set-up-custom-audiences-for-your-campaign) allow an advertiser to upload a UTF-8 CSV or text file containing email addresses, phone numbers, their SHA-256 hashes, or Google Advertising IDs. The system processes the file and reports an audience status. Uploaded rows are not the same as matched users: invalid, duplicate or unmatched identifiers do not count toward the matched audience.

An advertiser can include a ready audience to limit a campaign to matched users, exclude it to prevent delivery to those users, or adjust an ad group's maximum bid for matches. Inclusion and bid adjustments require at least **25,000 matched users**; smaller ready audiences can be used for exclusions. OpenAI recommends at least 100,000 users for inclusion or bid adjustments. Its documentation says Ads Manager does not reveal individual matches or let advertisers select a named person from the audience. A match does not guarantee that any particular ad appears, because other targeting and ad-selection conditions still apply.

OpenAI says uploaded audience files are deleted after processing, usually within 24 hours. It permits raw and pre-hashed email and phone values, but does not describe the internal treatment of raw values before matching. In 404 Media's account, OpenAI reiterated the available upload formats when asked about internal hashing. The company did not provide an answer to that narrower question.

## Access, cost and user controls

Ads are in a staged rollout for eligible Free and Go users; OpenAI says paid Plus, Pro, Business, Enterprise and Edu accounts have no ads. Advertiser self-service access depends on the billed entity's country, according to OpenAI's [availability list](https://help.openai.com/en/articles/20001245-ads-manager-availability). Its developer guide says custom audiences are unavailable for campaigns targeting the European Economic Area or Switzerland, where personalized ads are not yet available. Advertisers need an Ads Manager account, suitable rights to use the customer data and a campaign with billing set up. OpenAI lists a [**$25 minimum US-dollar daily campaign budget**](https://help.openai.com/en/articles/20001210-create-campaigns-for-chatgpt-ads); actual charges depend on the [campaign's delivery and billing model](https://help.openai.com/en/articles/20001216-billing-payment).

For users who see ads, [OpenAI says](https://help.openai.com/en/articles/20001047-ads-in-chatgpt) turning off personalization stops use of other chat threads, ad history and topics for ad selection, while ads may still reflect the current thread. Its Ads controls also allow users to view information about a placement and clear ads data. OpenAI says advertisers receive aggregate performance reports and cannot read users' conversations through the ads product. These are company statements about its system, not an independent audit of data handling.

## Sources & further reading

- [404 Media's October 15 investigation](https://www.404media.co/how-chatgpt-targets-ads-to-you-based-on-your-prompts-phone-number-and-email/). Joseph Cox describes the outlet's two ads, its context hint and its question to OpenAI about hashing. Its tests are the source for the reported observations.
- [OpenAI's Ads in ChatGPT FAQ](https://help.openai.com/en/articles/20001047-ads-in-chatgpt). Explains user eligibility, ad selection, personalization controls and the company's account of what advertisers receive.
- [OpenAI's custom-audience help article](https://help.openai.com/en/articles/20001346-set-up-custom-audiences-for-your-campaign) and [Ads API guide](https://developers.openai.com/ads/custom-audiences). Document accepted identifiers, list processing, matched-user thresholds, retention and regional limits. They do not settle internal hashing of raw uploads.
- [OpenAI's context-hint guidance](https://help.openai.com/en/articles/20001521-write-context-hints-for-chatgpt-ads). Explains how hints guide relevance without exact placement rules.
- [OpenAI's advertiser availability, campaign and billing guidance](https://help.openai.com/en/articles/20001245-ads-manager-availability). Identifies country-specific self-service access; the [campaign guide](https://help.openai.com/en/articles/20001210-create-campaigns-for-chatgpt-ads) supplies the USD daily minimum, and [billing guidance](https://help.openai.com/en/articles/20001216-billing-payment) describes how delivery is charged.

## Sources

- [How ChatGPT Targets Ads To You Based On Your Prompts, Phone Number, and Email](https://www.404media.co/how-chatgpt-targets-ads-to-you-based-on-your-prompts-phone-number-and-email/) — Joseph Cox reports 404 Media's two-ad test, context hint and OpenAI's non-answer on internal hashing; observations attributed to the outlet.
- [Ads in ChatGPT](https://help.openai.com/en/articles/20001047-ads-in-chatgpt) — OpenAI's account of eligibility, conversation context, personalization controls and advertiser reporting; exact page update date was not exposed in stable form.
- [Set up Custom Audiences for your Campaign](https://help.openai.com/en/articles/20001346-set-up-custom-audiences-for-your-campaign) — Official upload formats, processing, matched-user thresholds, retention and campaign controls.
- [Custom Audiences](https://developers.openai.com/ads/custom-audiences) — OpenAI Ads API guidance on accepted identifiers, eligibility, rights and regional availability.
- [Write Context Hints for ChatGPT Ads](https://help.openai.com/en/articles/20001521-write-context-hints-for-chatgpt-ads) — OpenAI's explanation that hints inform relevance without guaranteeing placement.
- [Ads Manager Availability](https://help.openai.com/en/articles/20001245-ads-manager-availability) — Country-specific advertiser self-service availability.
- [Create Campaigns for ChatGPT Ads](https://help.openai.com/en/articles/20001210-create-campaigns-for-chatgpt-ads) — Documents the $25 USD minimum daily campaign budget.
- [Billing & Payment](https://help.openai.com/en/articles/20001216-billing-payment) — Billing prerequisites and CPM/CPC or eligible conversion-optimized charging.