The rules
| Rule | Detail |
|---|---|
| Format | Hashed email addresses or phone numbers |
| Inclusion | At least 25,000 matched users |
| Exclusion | No minimum size (since 3 September 2026) |
| EEA and Switzerland | Avoid custom audiences; ads personalisation isn't available there |
Lists worth excluding
- Current customers. They don't need the ad and inflate costs.
- Your own staff and partners.
- Open deals already in late stages, unless you want to support them deliberately.
- Churned customers you don't want back.
When inclusion works
Inclusion makes sense for large lists: a big newsletter, a user base of a product-led tool, or event attendees over several years. Even then, the context hint still decides which conversations the ad appears in.
Keep lists current
Refresh exclusion lists monthly from your CRM. A customer who signed last week shouldn't see an ad this week.
How to prepare a list
- Export emails of customers, staff, partners and late-stage opportunities from your CRM.
- Remove duplicates and invalid addresses.
- Hash them as the platform requires, or let the upload tool hash them.
- Upload as an exclusion audience and apply it to every campaign.
- Set a monthly reminder to refresh it.
What match rates mean here
Not every email will match a ChatGPT user. Exclusions still help: every matched customer is one fewer wasted impression.
Questions
Can we include a list of target accounts?
Only as people, not companies, and only if 25,000 or more users match, which few ABM lists reach. Use your account list after the click instead.
Can we exclude competitors?
You can exclude people whose emails you have, but you won't have competitors' staff lists. Narrow hints do more.
Are customer lists safe to upload?
Lists are uploaded hashed. Check your privacy notice covers this use and that you have a lawful basis.
Why exclusions matter more than they seem
Customers and staff are among the most likely people to ask about your category, because they work in it. Without exclusions, a share of your budget goes to people who are already customers or colleagues. In narrow B2B categories, that share can be noticeable.
Beyond exclusions
Large lists, such as an active newsletter or a product's user base, can be used for inclusion if they reach 25,000 matched users. Use them for launches or upgrades aimed at people who already know you, in separate campaigns so they don't distort prospecting results.
Start here: ChatGPT ads for B2B. More articles in ChatGPT ads.