Similar Segments vs Optimized Targeting: What Replaced What
In short: These are two generations of the same idea: use what you know about good users to find more of them. Similar segments produced a visible artifact - a derived audience in your shared library you could apply, observe, bid on, or exclude. Optimized targeting, their designated successor since the 2023 sunset, produces nothing you can point at: it makes per-auction predictions aimed at your conversion goal and reports only in aggregate. The trade was transparency for conversion focus. If you came here looking for similar segments, the practical answer is to turn on optimized targeting and make sure your seeds and conversion tracking deserve the trust it will place in them.
By the AdFlint research team · Fact-checked against current Google and Meta platform behavior · Last reviewed July 2026
Optimized Targeting
Lets Google find additional converting users beyond the audiences you selected in a Display, Demand Gen, or Video campaign, treating your segments as a starting signal.
Enabled at the ad group level, it uses your chosen audiences and live conversion data as seeds, then bids on people outside those lists who look likely to convert. It is the intended successor to similar segments. It only behaves well when conversion tracking is reliable, and advertisers routinely confuse it with audience expansion, which widens reach without optimizing toward a conversion goal.
Full definitionSimilar 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 definitionSide by side.
The differences that actually change what happens in your account.
| Optimized Targeting | Similar Segments | |
|---|---|---|
| Status today | Live, and the default expansion path in Display, Demand Gen, and Video. | Removed in 2023 after a wind-down; nothing can apply one now. |
| The artifact it produces | None - decisions happen per auction and leave no audience object behind. | A named segment in the shared library, usable like any other list. |
| What seeds it | Your selected segments plus the campaign's live conversion data. | A single remarketing or Customer Match list per derived segment. |
| What it optimizes toward | The campaign's conversion goal - resemblance is only a means. | Resemblance to the seed, with no conversion objective inside the segment itself. |
| Controls available | An on/off toggle per ad group, and nothing finer. | Targeting or observation, bid adjustments, and exclusion, like any list. |
| Reporting visibility | Aggregate expansion rows - you see the total, never the composition. | Its own segment row with spend, clicks, and conversions attributable to it. |
| Bidding it worked with | Effectively inseparable from Smart Bidding and a tracked conversion goal. | Ran happily under manual CPC with adjustments layered on. |
What actually separates them.
Similar segments were an audience artifact and optimized targeting is a bidding behavior - you could point at one, you can only observe the other's aggregate results.
Similar segments chased resemblance whether or not resemblance converted, while optimized targeting aims at predicted conversions and treats the seed as a hint it is free to outgrow.
A similar segment could be excluded from other campaigns, while optimized targeting has no negative form - the only control is off.
Similar segments functioned under manual bidding, while optimized targeting presumes working conversion tracking and degrades badly without it.
The migration cost is visibility: switching on optimized targeting does not recreate segment-level reporting, so performance can hold while your ability to explain it drops.
Which one should you use?
Use Optimized Targeting when
- You want prospecting beyond your lists in a Display, Demand Gen, or Video campaign with a conversion goal.
- Your conversion tracking is reliable enough to be worth optimizing toward.
- You are modernizing an account that leaned on similar audiences before 2023.
- You accept aggregate reporting in exchange for expansion aimed at converters, not just lookalikes.
Use Similar Segments when
- You are auditing an account whose historical structure references similar audiences.
- You are reading older strategy material and need to translate it to current features.
- You are diagnosing why a legacy campaign's reach changed during 2023.
- You want a seed-based reach dial with a chosen audience size today - which points you at Demand Gen's lookalike segments, not here.
Common questions.
Is optimized targeting just similar audiences under a new name?
No. Similar audiences built a static-feeling derived list from one seed, while optimized targeting makes per-auction predictions aimed at your conversion goal, using your segments and live conversion data as inputs. The successor relationship is real, but the mechanics, controls, and reporting are all different.
Can I see who optimized targeting reached?
Not at any useful resolution. Audience reports show your named segments and an aggregate expansion line, and there is no per-user or per-derived-segment breakdown. If segment-level accountability matters to a stakeholder, that is a genuine loss versus the old similar segments and worth saying out loud before migrating.
I still want a real lookalike list - is there any option left?
Demand Gen campaigns offer lookalike segments built from your seed lists with a narrow, balanced, or broad reach choice, which is the closest surviving equivalent on Google - though by default they now function as a signal to Google's targeting AI rather than a hard cap, so treat the reach setting as guidance rather than a guarantee. Elsewhere, the combination of Customer Match seeds and optimized targeting is the intended path. Third-party lookalike building outside the platform cannot be applied as a Google Ads segment, so plan around what the platform actually accepts.
Do my old seed lists still do anything now that similar segments are gone?
Yes - they matter more, not less. Applied lists act as seeds that steer optimized targeting's predictions, and Customer Match uploads keep working as signals for Smart Bidding. Keep the lists fresh and segmented; a stale catch-all seed steers the machine toward stale lookalikes of the wrong people.
Or stop choosing between them.
AdFlint picks the setting, writes the ads, and keeps optimizing inside the Google and Meta accounts you already own.
Related comparisons
- Affinity Audiences vs In-Market Audiences
- Custom Segments vs In-Market Audiences
- Customer Match vs In-Market Audiences
- In-Market Audiences vs Remarketing Lists
- In-Market Audiences vs Similar Segments
- Demographic Targeting vs In-Market Audiences
- In-Market Audiences vs Life Events Targeting
- In-Market Audiences vs Optimized Targeting