Meta Custom Audiences: Sources and Rules

This guide is built from the Meta Business Help Center, checked on 10 November 2026: About custom audiences, About engagement custom audiences, Create a website custom audience, Troubleshoot website custom audience size, Create a customer list custom audience, Customer list formatting guidelines, Prepare your data for a customer list custom audience, About exclusion-only custom audiences, How to use custom or lookalike audiences and the other Help Center pages linked below. Meta renames and moves these settings often, so check the pages before you rely on a detail.

What a custom audience is

Meta describes a custom audience as one that "lets advertisers build audiences from their own data sources or Meta engagement data for retargeting campaigns, new customer campaigns and other ad targeting options." You can include it in an ad set to reach those people, exclude it to keep them out (for example, existing customers in a campaign for new ones), or use it as the source of a lookalike audience. An ad account can hold up to 500 custom audiences.

Our guide to remarketing audiences compares Meta's custom audiences with Google's data segments and covers consent. This page goes deeper into Meta's side: each source, its settings, and the rules that decide whether an audience can be used.

The sources Meta offers

Meta splits custom audiences into two groups: people who interacted with your business, and people who interacted with your content on Facebook, Instagram, WhatsApp and Threads.

Source	Who it contains	Group
Website	Visitors and their actions, tracked by the Meta Pixel	Your sources
App activity	People who took specific actions in your mobile app	Your sources
Catalog	People who interacted with items in your product catalog	Your sources
Customer list	Customers matched from uploaded emails, phone numbers and other identifiers	Your sources
Offline activity	People who bought in store or interacted with you offline	Your sources
Video	People who watched your videos on Meta platforms	Meta sources
Lead form	People who opened or submitted a lead form in your ads	Meta sources
Instant Experience	People who interacted with your full-screen Instant Experience ads	Meta sources
Shopping	People who browsed or bought from your Facebook or Instagram Shop	Meta sources
Instagram account	People who interacted with your Instagram professional account	Meta sources
Events	People who responded to your Facebook Events	Meta sources
Facebook Page	People who interacted with your Facebook Page	Meta sources
On-Facebook listings	People who interacted with your listings on Facebook Marketplace	Meta sources

Meta calls the second group engagement custom audiences, because they are built from actions such as "viewing videos, following a Facebook Page or opening a form in a lead generation ad". The difference from a website audience is where the action happens: on Meta's apps rather than on your site.

Website custom audiences

A website audience needs an active Meta Pixel. In Ads Manager you go to Audiences, choose Create audience, then Custom audience, then Website. You then choose whether people must meet Any or All of your criteria, pick the pixel, and pick the events. For "People who visited specific web pages" you can type URLs; Meta advises using "the minimum needed to distinguish the page", because not everyone loads a site with https or www.

Three settings matter most:

• Audience retention in days: how long a visitor stays in the audience after the qualifying visit or event.
• Rules: you can include more people or exclude people, with "up to 5 rules per audience".
• Start date: the audience "starts populating from the time you create it (ie, it won't backfill)".

The audience updates on its own as people reach the pages your rules cover, and Meta "may also add to your audience using on-platform events". Before you can use it, its status in Audiences must show Ready.

Why the audience is smaller than your visitor count

Meta's audience size troubleshooting page gives the reasons. Visitors only count if they also use Meta's apps, and Meta does not include accounts that have opted out of online behavioral advertising. Pixel fires are not unique visitors: one person can fire many events but is counted once. Meta's own example takes 20,000 visitors who viewed 7 pages each and says the audience "may be closer to 3,000 unique visitors". Events from some iOS 14 users may also be missing. The estimated size column can show Unavailable or Populating even when the audience is Ready, where Meta cannot show the size for privacy reasons.

If the audience is still too small, Meta suggests waiting until it holds several hundred people, using fewer conditions (or "Anyone who visits your website"), or making the retention window longer.

Customer list custom audiences

A customer list audience is built from details you collected from customers, which Meta calls identifiers. Meta hashes them before use, then matches the hashed values to profiles on its platforms. Meta says it "doesn't learn any new identifying information about your customers from hashed data".

To create one you must own the ad account or have admin or advertiser permission on it, and the ad account must be connected to a business portfolio. Meta warns that a new or recently linked account "may take a few weeks" before it can create or share customer list audiences.

Formatting the file

Meta's formatting guidelines say a customer list should be a CSV or TXT file, "include at least 1,000 customers", include at least one main identifier, and use the right column format for each identifier type. The main identifiers are:

• Email (column header email): up to 3 columns, one address per cell.
• Phone number (phone): up to 3 columns, always with the country code, "even if they're all from the same country".
• Mobile advertiser ID (madid): Android's advertising ID or Apple's IDFA.
• Facebook app user ID (appuid) and Facebook Page user ID (pageuid).

Optional columns such as first name, last name, city, county or region and country can improve the match when used with a main identifier. Meta asks for first and last names in separate columns, and for the country in its own column, as an ISO two-letter code, even if all your data comes from one country. An optional numeric value column (no currency symbols) lets you build a value-based lookalike later.

Match score and Outdated status

After the upload, the Audiences tab can show a Match score: "a score out of ten" for how well the list matched profiles, shown in steps of 0.5 and "calculated by dividing matched rows by uploaded rows". Adding more emails, phone numbers and device IDs can raise it. A list shows Outdated when it "has not been updated in over 30 days which may impact ad delivery"; use Update list to refresh it. In the ad set, a warning icon next to the audience can flag an Outdated list, a low match score or an audience that is too small.

Under the GDPR, Meta says the advertiser acts as the data controller for any list uploaded. Before an upload, read Meta's Customer List Custom Audiences Terms; our remarketing guide summarises them along with consent.

What a customer list must not contain

Meta's data preparation page says the names you choose, the data you include and the criteria behind a customer list "must not reflect, imply or be based on any prohibited information about people". Its examples, which it says are not a complete list, include:

• People who opted out of having their information used for ad audiences, where you committed to honour that.
• Information you know, or should reasonably know, is from or about children under 13.
• Identifiers Meta does not permit, such as Social Security numbers, passwords, GPS coordinates and public services identifiers.
• Financial account or status details, such as card numbers, credit scores, loan decisions and debt status.
• Physical or mental health information, such as conditions, treatments, prescriptions and places of treatment.

So a list named "customers with diabetes" or "people refused a loan" breaks the rules even if the file holds only emails. Meta's page on restrictions on certain custom audiences explains that audiences with such information are flagged and cannot be used for new campaigns (see flagged audiences below).

Exclusion-only audiences

When you add a customer list, you choose whether it is for "Inclusions or exclusions" or "Only exclusions". An exclusion-only custom audience can only keep people out of an ad audience. Meta suggests it for people who opted out of or self-excluded from your services, people "you have a legal or regulatory obligation not to target", and as "a permanent guardrail against accidental inclusion". If anyone in the ad account tries to include it, it appears greyed out.

	Regular custom audience	Exclusion-only custom audience
Include people	Yes	No
Exclude people	Yes	Yes
Source for a lookalike or value rules	Yes	No
Change to the other type later	–	No
Campaign types	All	All except Special Ad Categories (housing, employment, credit or financial products and services)

App activity audiences

An app activity audience needs a registered app that logs app events through the Meta SDK, or through a Meta Mobile Measurement Partner. Meta says an event "can be one of 14 pre-defined events" such as added to cart or level achieved, or a custom event of your own. You pick the app and the events, can include or exclude people by event, and set a retention period. Meta says the audience "is ready to use immediately, but it may take up to an hour" to fill with past users who logged a matching event. In an App promotion campaign, Meta's instructions note you can only use a custom audience as an audience suggestion.

Engagement audiences and retention

Every engagement audience uses a rolling window. Meta's example: with 30 days of retention, someone who engaged 29 days ago is in the audience, and if they do not engage again the next day, they drop out. New engagers are added all the time, so "you do not need to edit it or create a new one" unless you want a different window or engagement type. Source by source:

• Facebook Page: Meta's steps default to "Everyone who engaged with your Page"; retention "must be 365 days or less", and you can add up to 4 further criteria. Meta suggests including Page engagers for retargeting, or excluding them from a prospecting campaign.
• Instagram account: only an Instagram professional account (business or creator) can be the source, not a personal account. Retention is a "Maximum of 365 days". Meta notes that "exclusionary rules override inclusionary ones" (source).
• Video: you choose an engagement level, such as people who watched at least 10 seconds, and up to 200 videos from a Page, an Instagram professional account, a campaign or video IDs. If the ad reused an existing post, the audience may reflect the post's views rather than the ad's: Meta's example shows 1,000 views in the audience for a campaign with over 200,000 (source).
• Lead form: you choose the type of form engagement, the Page and the form, then the retention (source). This suits retargeting people who opened a lead ad form but did not submit it.

If the Facebook Page behind an engagement audience is deleted, Meta's page on expiring audiences says ad sets using it have 30 days to update or remove it. After that, those ad sets are paused and the audiences, including lookalikes and saved audiences built on them, are deleted automatically.

Audience labels

When you create or edit a customer list, website or app audience, you can add an audience label. The engaged-audience labels are Qualified leads, Disqualified leads, App users, Trial users and Other engaged users; the customer labels are High value, Low value, At risk, Disengaged and General customers. Meta says labels can help it find audiences for your ads, for example through value rules, and advises: "Only choose an audience label if these definitions fit your needs."

Suggestion or hard limit

How a custom audience behaves depends on where you add it in the ad set. Added under audience suggestions, Meta says "we will show ads to people matching your suggestion, and other audiences when it's likely to improve performance". Meta calls this Advantage+ custom audience. To restrict delivery to the audience, add it under the option to further limit your audience or reach and untick "Use as a suggestion". Exclusions are set as controls. Locations, minimum age and languages still apply either way.

Our rule of thumb: for a true retargeting campaign, use the audience as a limit; for prospecting, use it as an exclusion or a suggestion. Our guides to Advantage+ campaigns, Advantage+ audience and lookalike audiences cover the broader settings. Two more rules from Meta's pages:

• Meta recommends "that your custom audience includes at least 1,000 customers"; smaller audiences may affect delivery.
• For audiences that include people under 18 (or older in some countries), targeting is limited to location, age and gender, and custom audiences cannot be used to target those age groups.

Flagged, shared and expiring audiences

Flagged audiences. If Meta finds information that is not allowed under its terms, such as a health condition or a credit score, the custom audience and any lookalike built on it are flagged. You cannot use a flagged audience for new campaigns, and Meta advises editing or pausing active campaigns that use one. To fix it, remove the information, build a new audience or pick another one. If you think the flag is a mistake, you can request a review in Ads Manager or in the audience's summary tab. Meta adds that these checks "aren't a substitute for your own compliance mechanisms".

Sharing. Meta lets you share custom audiences between ad accounts when both sides belong to a business portfolio. Someone with full control of the sharing portfolio starts it, and someone with full control of the receiving portfolio accepts a one-time partnership request. A shared audience cannot be used to create a lookalike. This suits an agency and a client who keep separate ad accounts.

Expiring audiences. As above, audiences built on a deleted Facebook Page stop working after 30 days. In Audience Manager, filter Availability for Error to find them.

How we build custom audiences

This is our own working practice, not Meta's wording.

• We create the website audiences a client is likely to need (all visitors, key pages, purchasers or leads) on day one, because they do not backfill.
• We name audiences after the action and window, such as "Web - pricing page - 30d", never after anything that could read as sensitive.
• Customer lists are exported from the client's CRM with only the columns Meta needs, phone numbers with country codes, and refreshed before they reach 30 days.
• Opt-outs and anyone the client must not target go into an exclusion-only list.
• In each ad set we check whether the audience is a suggestion or a limit before launch, because that decides whether the campaign is retargeting at all.

Frequently asked questions

How many people does a Meta custom audience need?

Meta's formatting guidelines say a customer list should include at least 1,000 customers, and its targeting help recommends at least 1,000 customers in a custom audience because a small one may affect delivery. For a website audience that is still small, Meta suggests waiting until it holds several hundred people.

How long can people stay in a custom audience?

You set the retention in days. For Facebook Page and Instagram account audiences the maximum is 365 days. Engagement audiences use a rolling window, so people drop out once their last engagement is older than the window.

Why does my website custom audience not include past visitors?

Meta says a website custom audience starts populating from the time you create it and won't backfill. Create the audiences you expect to need as soon as the Meta Pixel is live.

What does Outdated mean on a customer list?

The list has not been updated in over 30 days, which Meta says may impact ad delivery. Use Update list in Audiences to refresh it.

Can I use a custom audience only to exclude people?

Yes. Create a customer list and choose Only exclusions. The audience can then only be used as an exclusion, cannot be changed back and cannot be a lookalike source. It is not available for campaigns under Special Ad Categories.

For more on Meta ads, see our guides to remarketing audiences, lookalike audiences, the Meta Pixel and Conversions API, Advantage+ campaigns, Special Ad Categories and Meta ads basics.