Audience Targeting

Custom Segments vs Remarketing Lists: New Prospects or Past Visitors

In short: Both are audiences you build yourself rather than pick off Google's prebuilt shelf. Custom segments describe a behavior pattern to find people who look like your buyer but have never touched your site. Remarketing lists are built from people who already visited your site, used your app, or watched your video, a warm list rather than an inferred one. Custom segments do prospecting; remarketing does retargeting against existing intent aimed at you specifically. If the person has never interacted with your brand, use custom segments; if they have, use remarketing and layer it onto Search as RLSA.

By the AdFlint research team · Fact-checked against current Google and Meta platform behavior · Last reviewed July 2026

Custom Segments

Lets you define your own Google audience from keywords people search, websites they browse, or apps they use, instead of picking a prebuilt segment.

You supply search terms, URLs, or app IDs, and Google assembles an audience of people whose behavior matches those signals across Display, Video, and Demand Gen. It is the closest thing to keyword targeting outside Search, and it replaced the older custom affinity and custom intent segments. Most accounts overload one segment with unrelated inputs, which blurs the signal Google builds against.

Full definition

Remarketing Lists

Audience lists built from people who already visited your site, used your app, or watched your videos, applied for targeting or bid adjustments in Google Ads.

A Google tag or linked Analytics property collects visitors into rule-based lists - all users, cart abandoners, a specific URL path - which you apply to Display, Video, Demand Gen, or Search campaigns as RLSA. Lists must clear minimum sizes before they serve. Most advertisers build one catch-all list and stop; segmenting by page depth and recency is where the performance difference actually lives.

Full definition

Side by side.

The differences that actually change what happens in your account.

 Custom SegmentsRemarketing Lists
Who's in the audienceStrangers who show a described behavior pattern.People with a tracked visit, app use, or video view tied to your own tag.
Data sourceKeywords, URLs, or apps you specify, interpreted by Google.Your own Google tag or linked Analytics property collecting real visitors.
Relationship to your businessNo prior contact required.Always has at least one prior touchpoint with your property.
Runs on SearchNo.Yes, as RLSA, alongside Display, Video, and Demand Gen.
List minimumNot a hard gate, a narrow input just limits reach.Must clear a minimum size before Google will serve it.
Segmentation leverRefining the input keywords, URLs, or apps.Rule logic such as page visited, cart abandonment, or recency window.
Typical funnel stageTop of funnel, prospecting.Middle to bottom of funnel, a warm audience.

What actually separates them.

01

Custom segments infer an audience from behavior you describe, while remarketing lists are built only from tracked visits to your own site, app, or videos, so remarketing never contains a stranger.

02

Remarketing lists can run on Search as RLSA to adjust bids or narrow a Search campaign to past visitors, while custom segments have no Search application at all.

03

A custom segment's quality depends on how well your keywords or URLs describe the behavior you want, while a remarketing list's quality depends on how your rules slice visits by page, action, or recency.

04

Remarketing lists need your tag firing correctly and enough traffic to accrue before they are usable, while custom segments can be created and used immediately since they draw on Google's own data, not your traffic.

05

You typically exclude converted users from a remarketing list to stop showing ads to existing customers, a suppression pattern that does not apply to custom segments since nobody in one has converted with you yet.

Which one should you use?

Use Custom Segments when

  • You want to reach net-new people who have never visited your site but show the right behavior pattern elsewhere.
  • Your site does not have enough traffic yet to build a usable remarketing list.
  • You are expanding into a new market or product line with no existing visitor base to draw from.
  • You want an audience Google keeps refreshing against ongoing behavior rather than a fixed visit log.

Use Remarketing Lists when

  • Someone visited a specific product page or added to cart and did not convert, and you want to bring them back.
  • You want a bid adjustment or narrower keyword set on Search specifically for past site visitors.
  • You are segmenting by recency, visited in the last 7 days versus 30, to match urgency to messaging.
  • You want to exclude recent purchasers from campaigns still chasing the same conversion.

Common questions.

How long does it take for a remarketing list to be usable?

It depends on how fast your traffic accrues enough matched users to clear Google's minimum list size, not a fixed number of days. A low-traffic site might take weeks to build a workable list, while a high-traffic site clears it in a day or two.

Can I use a custom segment as a remarketing audience?

No, they are built from different data. Custom segments come from Google's read of behavior signals you describe, while remarketing lists come from actual tracked visits to your property. You can run both in the same ad group as separate layers, but one does not substitute for the other.

What's RLSA and is it different from remarketing?

RLSA is remarketing lists for search ads, the same remarketing lists applied to Search campaigns instead of Display or Video, used to adjust bids or narrow targeting to past visitors when they search again. It is the same underlying list, just a different campaign type using it.

Why isn't my remarketing list showing any audience size?

Most commonly the tag isn't firing correctly, the list's membership duration excludes older visits, or traffic simply hasn't been enough to clear the minimum size Google requires before a list activates. Check tag health first, since that silently breaks more lists than any rule misconfiguration.

Or stop choosing between them.

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