How to set up Google Ads remarketing with GA4 and GTM (2025 guide)

Google Ads remarketing runs on three pieces wired together: GA4 collects behaviour, GTM fires the Google Ads remarketing tag, and Google Ads pulls the audience from GA4 to target the right people. If any one of those three is broken or misconfigured, you either show ads to nobody, show ads to the wrong people, or quietly lose 30-40% of your audience to Consent Mode v2. This guide walks through the exact setup I use on client accounts, including the Consent Mode v2 step most tutorials skip.

This is for marketers running Google Ads and GA4 who want to build a working remarketing pipeline once and stop worrying about it. If you are only interested in "click here, check that box", you will find a shorter version at the top of each step. If you want to know why a step exists, keep reading.

What Google Ads remarketing actually is in 2025

Remarketing is showing ads to people who already interacted with your site. Someone added a product to cart and left. Someone read a pricing page twice in a week. Someone signed up for a trial but never logged in. Remarketing reaches them again on Google Search, Display, YouTube, or Discover.

The setup changed significantly in 2024. The legacy AdWords Remarketing tag (conversion_id + remarketing_only) still fires, but the modern default is:

1. You define the audience in GA4 (using events, page views, user properties, or predictive signals).
2. You link the GA4 property to the Google Ads account.
3. Google Ads sees the audience in its Shared Library and lets you target it in a campaign.

The GTM remarketing tag is still worth firing for three reasons: dynamic remarketing (product IDs), cross-domain tracking, and anything you want to send to Google Ads that is not already a GA4 event. In most accounts I run, both approaches coexist.

When remarketing is worth the effort

Not every business benefits. You need three things:

• Traffic: a minimum of 100 qualifying users per audience per month. Low-traffic B2B sites often fall short.
• A clear conversion path: cart abandonment, trial signup, demo request. "General brand awareness" remarketing tends to burn budget with no measurable return.
• Creative variation: serving the same static banner for 90 days is the fastest way to trigger ad blindness. Plan at least 3-4 creative variants per audience.

If any of those are missing, spend the budget on prospecting and come back to remarketing later.

How the GA4 to GTM to Google Ads pipeline works

Before the clicks, understand the flow. A user lands on your site. GTM fires the GA4 config tag, which sends a page_view event with parameters. GA4 ingests the event and matches it against any audience definition you created. If the user qualifies, GA4 adds them to the audience. Because GA4 is linked to Google Ads, the audience is shared across to Shared Library. A campaign targeting that audience can now bid for that user when they appear on the Google Display Network, YouTube, or Search.

At the same time, if you have the Google Ads Remarketing tag configured in GTM, it fires its own cookie (_gcl_aw) and sends the user to a Google Ads remarketing list directly. This is the legacy path. It still works and is useful when you need immediate signal (audience updates in GA4 can take up to 24h).

Two paths, one user, same destination. Both layers fail without Consent Mode v2 consent flags set correctly, which is why I put that step inside the main setup rather than treating it as an afterthought.

Step 1: Build the audience in GA4

Go to GA4 > Admin > Audiences > New audience. You will see templates (Suggested audiences, General, Templates, Predictive) and a "Create a custom audience" option. Custom is where the real work happens.

Start with cart abandoners

A typical e-commerce remarketing audience is "added to cart, did not purchase in the last 14 days". In GA4 this is:

• Include: users where the event add_to_cart occurred.
• Exclude: users where the event purchase occurred in any session.
• Membership duration: 14 days (or 7 if inventory is small, 30 if the purchase cycle is long).

Click Save. GA4 will start populating the audience immediately for new users, but existing qualifying users only appear after GA4 has enough historical data. Give it 24-48h before you check the audience size.

Five audiences worth building on day one

Copy these into every GA4 property you run.

1. Cart abandoners - add_to_cart AND NOT purchase, 14 days.
2. Checkout started, not completed - begin_checkout AND NOT purchase, 7 days.
3. Engaged pricing-page viewers - page_view on /pricing AND session duration > 30s, 30 days.
4. Trial signups without activation - sign_up AND NOT custom event first_value_action, 14 days.
5. High-intent returning visitors - at least 2 sessions AND viewed a key page, 30 days.

The last one is the workhorse on B2B SaaS accounts. It captures people who are researching but not ready to convert.

Audience size matters

Google will not serve remarketing ads to an audience smaller than its minimum threshold. For 2025 those are:

• Display Network: 100 active users in the last 30 days.
• YouTube: 1,000 active users.
• Search (RLSA): 1,000 active users.
• Gmail: 100 active users.

If your audience is below threshold, widen the criteria (longer lookback, less strict exclude) or combine two audiences. Do not launch a campaign targeting an under-threshold audience and wonder why impressions are zero.

Step 2: Link GA4 to Google Ads

In GA4 > Admin > Product links > Google Ads links > Link, pick the Google Ads account and confirm. Enable "Personalised advertising" so the audiences flow through. If you skip this toggle, audiences are visible in GA4 but empty in Google Ads Shared Library.

Give it 24 hours. Google Ads rebuilds the Shared Library once per day. If the audience does not show up after 48h, check:

• Your GA4 property has "Google signals" enabled (Admin > Data Settings > Data Collection). Without it, audiences cannot cross to Ads.
• You have admin rights on both the GA4 property and the Google Ads account. Editor alone is not enough for product links.
• The Google Ads account is not in "paused" state. Paused accounts still accept links but do not sync audiences.

This is the stage where I see most "my audience is empty" tickets. 90% of the time, Google signals is off.

Step 3: Configure the Google Ads Remarketing tag in GTM

The GA4 audience path covers most cases. For dynamic remarketing (showing the exact product a user viewed), you need the Google Ads Remarketing tag with custom parameters. This lives in GTM.

Create the tag

In GTM:

1. Tags > New > Tag Configuration > Google Ads Remarketing.
2. Conversion ID: your Google Ads conversion ID (AW-XXXXXXXXX). Find it in Google Ads > Tools > Conversions > the little code snippet at the bottom.
3. Conversion Label: usually blank for remarketing (labels are for conversion tracking).
4. Custom Parameters: add ecomm_pagetype, ecomm_prodid, ecomm_totalvalue if you run dynamic remarketing. Leave empty if not.
5. Trigger: All Pages (or All Pages minus thank-you pages if you want to exclude converters from being retargeted).

Wire up the data layer for dynamic remarketing

If you run dynamic product ads, the Google Ads Remarketing tag needs product IDs in the data layer. A clean implementation pushes this from the site:

dataLayer.push({
  'event': 'view_item',
  'ecomm_prodid': ['SKU-4821'],
  'ecomm_pagetype': 'product',
  'ecomm_totalvalue': 129.00
});

Then in GTM create three Data Layer Variables (dlv_ecomm_prodid, dlv_ecomm_pagetype, dlv_ecomm_totalvalue) and map them into the custom parameters of the remarketing tag. Test with Google Tag Assistant. The request payload should show the product ID.

Test before you publish

GTM Preview mode is mandatory here. Load a product page, check the Google Ads Remarketing tag fired, then inspect the network request in Chrome DevTools. You are looking for a call to googleads.g.doubleclick.net/pagead/viewthroughconversion/... with your product ID in the query string. If you do not see the product ID, your data layer variables are wrong, not the tag.

Step 4: Consent Mode v2 is where remarketing quietly breaks

This is the step most blog posts skip. Consent Mode v2 passes four signals from your cookie banner to Google tags: ad_storage, ad_user_data, ad_personalization, and analytics_storage. Without the first three set to granted, your Google Ads Remarketing tag will fire in cookieless mode. The user enters your GA4 audience but Google cannot match them for remarketing purposes.

On EU accounts, 30-40% of users decline consent. Without Consent Mode v2 wired correctly, that 30-40% is invisible to your remarketing list. You lose addressable audience, the list shrinks below threshold, campaigns stop serving.

Minimum Consent Mode v2 setup for remarketing

Your CMP (Cookiebot, OneTrust, Usercentrics, Cookie Banner Pro) must push the following on consent change:

gtag('consent', 'update', {
  'ad_storage': 'granted',
  'ad_user_data': 'granted',
  'ad_personalization': 'granted',
  'analytics_storage': 'granted'
});

If the user denies consent, these stay at denied and Google Ads collects a cookieless ping for modelling but does not add them to remarketing lists.

For a deep dive on wiring this correctly, see my Consent Mode v2 implementation guide. For the consent-timing race condition that breaks most installs, use the Universal Consent Adapter, my free GTM template that reads consent state before the CMP JavaScript loads.

Advanced vs Basic Consent Mode

Advanced Consent Mode fires tags with anonymous pings even before consent is given, allowing Google to model denied-consent users back into your conversion data. Basic blocks everything until consent is granted.

For remarketing, Advanced is almost always the right choice in the EU. Modeled conversions are imperfect, but "some signal" beats "no signal". Do not run Basic mode if you care about remarketing volume.

Step 5: Launch the remarketing campaign

Google Ads > Campaigns > New > Sales (or Leads, or Website traffic). For remarketing, Display or Performance Max are the usual choices. At the audience step:

1. Audience segments > Browse > How they have interacted with your business.
2. Pick the GA4 audience you created in Step 1.
3. Set targeting to "Observation" first (not Targeting) to see who Google finds. Switch to Targeting once you trust the audience.
4. Budget: start small. €10-€20/day for the first 14 days is enough to generate signal without wasting budget on a misconfigured list.
5. Creative: 3-4 variants minimum. Ad fatigue kicks in fast on remarketing.

Frequency capping

Default frequency caps on Display are usually too loose. Set 3-5 impressions per user per day maximum. Anything above that and your CPM climbs, your CTR drops, and brand sentiment suffers. "How is this ad following me around" is the exact sentiment you want to avoid.

Common remarketing mistakes I see on client accounts

1. Google signals off in GA4. Audiences never reach Shared Library. Always check Admin > Data Settings > Data Collection.
2. Conversion ID wrong in GTM. Someone copied the conversion ID from the wrong Google Ads account. Double-check the AW-XXXXX prefix matches.
3. Consent Mode v2 misconfigured. The CMP is not pushing the four signals, or is pushing them before GA4 initialises. Use the Universal Consent Adapter to fix the timing.
4. Audience too narrow. "Visited page X AND did Y AND viewed Z" audiences often fall below the minimum threshold. Start broader, narrow later.
5. No exclude on converters. Showing remarketing ads to people who already bought is how you get support tickets. Always exclude the purchase event from remarketing audiences, or add a converter audience to the campaign's exclusion list.
6. Creative never rotated. Three months on the same banner = trained blindness. Rotate every 30-45 days.
7. Frequency caps left at default. Google's defaults are set for reach, not sanity. Tighten them.
8. Skipping GA4 audiences because "the remarketing tag is enough". The GTM tag works, but you lose the audience granularity GA4 gives you.

The most expensive of these is number three. I have audited accounts where the GA4 remarketing list looked healthy at 80,000 users, but Google Ads only saw 35,000 because Consent Mode v2 was denying storage to everyone who clicked Reject on the cookie banner. The client was paying for a campaign that could only reach less than half its audience.

Frequently asked questions

How long does it take for a GA4 audience to appear in Google Ads?

Usually 24-48 hours after you link the two accounts and enable Google signals. If it is still empty after 72h, something is wrong. Check Google signals, permissions, and that the GA4 property is actually collecting data.

What is the minimum audience size for Google Ads remarketing?

100 active users in the last 30 days for Display and Gmail. 1,000 for YouTube and Search RLSA. Below that, Google will not serve ads to protect user privacy.

Does remarketing still work in the EU with GDPR and Consent Mode v2?

Yes, but only for users who granted consent. Without Consent Mode v2 Advanced mode, you lose 30-40% of EU users from remarketing lists. With Advanced mode and modeling enabled, Google reconstructs some of the lost signal. This is also covered in my Google Analytics and GDPR guide.

Do I still need the Google Ads Remarketing tag if I have GA4 audiences linked?

For standard remarketing, no, GA4 audiences are enough. For dynamic remarketing (product-level ads), yes, you need the GTM tag with custom parameters. For the cleanest setup, run both.

How is remarketing different from retargeting?

Same concept, different vocabulary. Google uses "remarketing", Meta and most other platforms use "retargeting". The underlying mechanic is identical: ads served to people who already interacted with your site.

Why are my remarketing impressions so low?

Four common causes: audience below minimum threshold, Consent Mode v2 killing consent signal, conversion ID wrong in GTM, Google signals off in GA4. Work through them in that order.

Can I use GA4 audiences for Performance Max?

Yes, and you should. PMax uses audience signals as a seed, not strict targeting. A well-built GA4 audience (cart abandoners, high-intent visitors) gives PMax a meaningful signal to find similar users on.

Next steps

If you already have GA4 and GTM installed, you can have your first remarketing campaign live inside an afternoon. The 45-90 minute estimate in the key takeaways assumes the data layer is clean. If your site pushes inconsistent events, budget another day for cleanup.

Most of the time when I get pulled into a remarketing problem, the actual issue is not the campaign. It is Consent Mode v2 misconfiguration, a broken data layer, or GA4 audiences that were never validated. Before you add more budget, verify the tracking. I built the Free GTM Audit for this exact check. It runs in 10 minutes, no signup, and flags Consent Mode v2 issues, broken tags, and common data layer problems.

If the audit flags more than a handful of issues, or you want ongoing monitoring so remarketing does not quietly break next time your CMS updates, my GTM monitoring retainer starts at €150/month with weekly automated health checks and a monthly written report.

Either way, fix the pipe before you pour more water into it.