Audience Targeting

Custom Segments vs Similar Segments: Why One Was Retired

In short: Both once sat in Google's audience menu, but only one still exists. Custom segments are the live tool for defining your own audience from keywords, URLs, or apps you specify. Similar segments were Google's automatic lookalike expansion built from a remarketing or Customer Match seed, and Google retired them in 2023 in favor of automation built into targeting and bidding themselves. If you are looking for similar segments today, what you actually want is optimized targeting or an audience signal feeding Smart Bidding. There is no live choice here, only a live tool and its retired predecessor, so build with custom segments and lean on optimized targeting for the expansion job similar segments used to do.

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

Similar Segments

Google's retired audience expansion feature, which generated lookalike-style segments from a seed list before being removed in 2023 in favor of automated targeting.

Similar segments once derived a resembling audience automatically from a remarketing or Customer Match seed, and Google sunset them so campaign-level automation could do that expansion instead. Your seed lists remain valuable as signals feeding optimized targeting and Smart Bidding rather than as sources for a derived list. Advertisers still hunting for the setting almost always want optimized targeting or Customer Match.

Full definition

Side by side.

The differences that actually change what happens in your account.

 Custom SegmentsSimilar Segments
Current statusFully active, available today in every eligible campaign type.Retired by Google in 2023, no longer available to create or edit.
What it neededKeywords, URLs, or app IDs you supply directly.An existing remarketing or Customer Match list to use as a seed.
How the audience formedGoogle matches people whose behavior fits the inputs you stated.Google auto-generated a lookalike audience resembling your seed list, without you specifying behavior.
What replaced itNot applicable, it is the current tool.Optimized targeting and audience signals inside Smart Bidding absorbed the same job.
Where old campaigns land nowUnaffected.Any ad group that referenced a similar segment lost that targeting line when it was removed.
Effort required from youYou write the defining keywords, URLs, or apps yourself.None, expansion logic ran automatically off your seed list while it existed.

What actually separates them.

01

Custom segments are live and editable today, while similar segments can no longer be created, edited, or found in the interface since Google removed them in 2023.

02

Custom segments require you to describe the behavior directly through keywords, URLs, or apps, while similar segments never asked for that and simply auto-expanded from whatever seed list you pointed at.

03

Any campaign still structured around a similar segment silently lost that targeting line when the feature was pulled and needs to be rebuilt with a live alternative.

04

Custom segments feed a campaign as a targeting or observation layer you actively manage, while the expansion job similar segments used to do now runs automatically inside optimized targeting and Smart Bidding with no separate list to inspect.

05

A custom segment's quality is judged by how well your inputs describe the behavior you want, while there is no equivalent quality check for a similar segment since the audience was generated for you, not defined by you.

Which one should you use?

Use Custom Segments when

  • You want to define exactly which behaviors qualify someone for the audience.
  • You are prospecting for a described interest and do not have an existing seed list to expand from.
  • You are rebuilding targeting that used to rely on a similar segment and need a live replacement.
  • You want an audience you can inspect and edit the inputs for, rather than a black-box expansion.

Use Similar Segments when

  • You already have a strong remarketing or Customer Match list and want automatic expansion toward similar people; use optimized targeting or an audience signal instead.
  • You are reading old documentation or a legacy account and see similar segments referenced; know it is gone and any dependent targeting needs rebuilding.
  • You want lookalike-style expansion without hand-picking behavior signals; feed your best list into optimized targeting or Performance Max audience signals instead.
  • You inherited a campaign built years ago that still lists a similar segment as an audience; treat that line as dead weight and replace it.

Common questions.

Are similar segments coming back?

No, Google removed similar segments, also called similar audiences, in 2023 and folded that expansion logic into optimized targeting and Smart Bidding instead. There is no setting to re-enable them.

What do I use instead of similar segments now?

Optimized targeting is the direct successor. It uses your existing audiences and live conversion data to find additional people likely to convert, without you needing a manual lookalike list. Feeding a strong remarketing or Customer Match list as an audience signal into Demand Gen or Performance Max does similar work.

My ad group used to have a similar segment, why is it gone?

Google automatically removed similar segments from every campaign that used them when the feature was retired, so any ad group relying on one lost that targeting line without a manual swap-in. Check current audience settings and replace it with optimized targeting or a custom segment.

Is Customer Match audience expansion the same as similar segments were?

They are related but not identical. Similar segments generated a separate, addressable lookalike list from a seed, while today's expansion through optimized targeting or Customer Match's built-in expansion option works inside the campaign's own targeting and bidding rather than producing a standalone list you can view or edit.

Or stop choosing between them.

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