ChatGPT Ads custom audiences: file setup, eligibility and safe use

The short version

Custom audiences let an advertiser use its own customer or prospect list for campaign inclusion, campaign exclusion or an ad-group bid adjustment. Correct formatting is only one check: you also need the right to use the first-party data for advertising. An audience marked Ready may still be too small for every use.

The three ways to use an audience

OpenAI recommends at least 100,000 matched users for inclusion or bid adjustments. The 25,000 figure is the current minimum, not a guarantee: uploaded rows and matched people differ because files can include duplicates, invalid values or identifiers that cannot be matched. A small audience may show Ready with an “Exclusion only” note. Check eligibility for the intended use. Read OpenAI’s audience guide.

You can include and exclude audiences in the same campaign, but the same audience cannot be both. Exclusions take precedence, and the remaining eligible audience must still meet the inclusion threshold. A bid multiplier changes how competitively an ad group bids; it does not determine who is eligible. The current multiplier range is 0.1× to 10×. When multiple selected audiences match, OpenAI applies the highest matching multiplier.

Prepare the audience file

OpenAI currently accepts UTF-8 CSV and TXT files up to 500 MB. Supported identifiers are email, phone number, SHA-256 hashed email, SHA-256 hashed phone number, and Google Advertising ID (GAID).

• A CSV needs a header row with supported names such as email, phone_number, email_sha256, phone_number_sha256 or gaid.
• A TXT file contains one identifier per line; choose the identifier type when uploading.
• Phone numbers must use E.164 format, including + and the country code. For Pakistan, normalize a number to international +92… format rather than local 03… format.
• Before hashing an email, lowercase and trim it. Before hashing a phone number, normalize it to E.164 first. Hashing does not establish permission to use the data.

Create and check the audience

In Ads Manager, open Tools → Audiences, select Create audience, name it, upload the CSV or TXT file, review the detected details and create it. CSV headers can allow the interface to infer the identifier type. Check the current interface before preparing a large list.

Wait until processing is complete. “Processing” means the audience is not ready. “Ready” confirms that processing completed, but a list under the threshold may be limited to exclusion use. “Failed” means the file did not process; check UTF-8 encoding, supported identifiers, header names, file size and formatting. OpenAI says processing usually takes about 20–30 minutes, but timing varies.

After creation, you can add, remove or replace members without rebuilding campaigns and ad groups that use the audience. OpenAI says the uploaded file is deleted after processing, usually no later than 24 hours. That concerns the upload file; it does not mean the audience itself is deleted.

Use only data you have the right to advertise with

OpenAI’s developer documentation says to upload only first-party audience data that you have the right to use for ads, and not broker-sourced data. Before upload, confirm required rights, notices, consents, permissions and legal bases, follow the Ad Tools Terms, and get privacy or legal review for your use case. These platform requirements do not replace the rules that apply to your business or the people on your list.

Do not assume that an email collected for one purpose can automatically be reused for advertising. Do not upload scraped or purchased lists. Hashing is a format option, not permission to use the data. If the permitted use is unclear, review OpenAI’s developer guidance and consult your privacy or legal adviser.

Practical examples and regional limits

• Exclusion: Exclude a small recent-buyer list from a new-customer campaign, if your data-use rights cover that use.
• Inclusion: Reach a qualified segment only after it reaches the matched-user minimum and is eligible.
• Bid adjustment: Raise or lower an ad-group bid for an eligible audience without changing campaign inclusion.

Custom audiences are audience-level controls. Ads Manager does not reveal individual matched users or let an advertiser select a particular person. OpenAI currently says custom audiences are unsupported for campaigns targeting the European Economic Area or Switzerland while ads personalization is unavailable there. This was checked on 27 October 2026; recheck before planning a campaign in either region.

Common mistakes

• Uploading local-format phone numbers without the plus sign and country code.
• Assuming 25,000 uploaded rows means 25,000 matched users.
• Treating Ready as eligibility for inclusion or bid adjustment.
• Using a bid multiplier as if it restricted campaign eligibility.
• Setting the same audience as both included and excluded.
• Assuming hashing makes data collection or use automatically compliant.

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