Remarketing lists for search ads (RLSA) let you change how your Google search campaigns treat people who have visited your website or used your app before. When someone on one of your lists searches on Google, you can bid more for them, show them a different ad, or show ads only to them.
How RLSA works
You start with a remarketing list built from the Google tag, from GA4 or from Customer Match. You then add that list to a search campaign or ad group under one of two settings:
- Observation: ads still show to everyone searching your keywords. The list is used to report on how past visitors behave and, with manual bidding, to apply a bid adjustment for them.
- Targeting: ads show only to people on the list. Everyone else searching the same keywords sees nothing from that ad group.
Lists can also be excluded, so a campaign aimed at new customers stops appearing for people who have already bought. Google needs a minimum number of active users on a list before it will serve, so a small site may need longer membership durations to qualify.
If the campaign uses Smart Bidding, manual bid adjustments on audiences are ignored, because the system already takes list membership into account in each auction. Adding lists on Observation is still worthwhile, because it gives you the reporting.
Why it matters
Someone searching “boiler replacement cost” for the first time is a different prospect from someone who read your boiler page last week and is now searching again. RLSA lets you treat them differently. Typical uses include:
- Bidding harder on broad, expensive keywords only for past visitors, where the chance of an enquiry is higher.
- Running generic terms such as “accountant” that would waste money on cold traffic but make sense for people who already know you.
- Writing ads for returning visitors that pick up where they left off or give them a reason to come back.
- Excluding existing customers from campaigns meant to win new ones.
For a UK service business on a modest budget, that control can make expensive head terms affordable by limiting them to people already weighing up a decision.
The lists depend on consent. Under PECR, UK visitors who decline advertising cookies are not added, so RLSA audiences are smaller than your visitor numbers suggest.
Common mistakes
- Choosing Targeting when you meant Observation, which quietly cuts a campaign down to past visitors only.
- Setting bid adjustments in a Smart Bidding campaign and assuming they do something.
- Using short list durations that never reach the minimum size for search.
- Not excluding converters, so you pay for clicks from customers who were only searching for the login page.
- Judging RLSA on conversion rate alone. Returning visitors nearly always convert better; the real question is whether the extra bid brought extra sales.
How to act on it
Add your main lists to every search campaign on Observation first. After a few weeks, compare cost per conversion and conversion rate for listed visitors with everyone else. Where returning visitors perform much better, consider a separate Targeting campaign on broader keywords, with ads written for people who already know you.
Check list sizes in Audience manager, fix any that are too small to serve, and review your consent set-up so the lists grow lawfully. Building audience layers into search accounts is part of my search ads management.