Set up GA4 for Google Ads: property, key events and conversion import

Setting up GA4 takes half an hour, and it is still the place where most Google Ads numbers break later. Not because the tag is missing, but because the wrong events are marked as key events, values arrive without a currency, or the same enquiry counts twice as a conversion. Here is the setup in the order that matters for Google Ads, with the menu names from Google’s own help pages.

1. Set up GA4: property, data stream and Google tag

A property is the container for one website’s data. If you already have an Analytics account, you only add a new property to it.

1. In GA4, click Admin, then Create, and select Property.
2. Enter a name and pick the reporting time zone and currency. I use the same time zone and currency as the Google Ads account, so daily figures and amounts line up. According to Google, changing the time zone later only affects future data.
3. Click Next, pick your industry category and business size, click Next again and choose how you intend to use Google Analytics. This mainly decides which default reports you see.
4. Click Create.

Next comes the data stream. In Admin, under Data collection and modification, click Data Streams, then Add stream and Web. Enter your website URL and a stream name, leave enhanced measurement switched on and click Create stream. Under Stream Details you now see the Measurement ID starting with “G-”.

Add the Google tag

For data to flow, the Google tag has to load on every page. Many shop systems and site builders have a field for the Google tag ID: paste the G-ID there. If you use Google Tag Manager, the German version of Google’s help describes this route:

1. Tags → New → under Choose tag type select Google Tag.
2. Enter the G-ID under Tag ID.
3. Set the trigger to Initialization - All Initialization Events and save.
4. Check in Preview that the tag fires, then publish.

The English version of the same help page now recommends a second route via a Google Analytics destination: under Tag Configuration choose Google Analytics → Google Analytics and enter the Tag ID there. The trigger is the same. If your container offers this option, use it. If you’d rather not click the structure together yourself, my free GTM configurator does the groundwork. What Tag Manager can and can’t do in general is covered in the Google Tag Manager guide.

Two settings to change on day one

Data retention. Under Admin → Data Settings → Data Retention, a standard property lets you set Event data retention to 2 or 14 months. Choose 14. According to Google, this setting doesn’t affect standard reports, only explorations and funnel reports. That is exactly where you’ll look a year from now when you want to know how visitors from one keyword behaved. Extending the period only applies to data that hasn’t been deleted yet, so do it on the first day.

Internal traffic. Your own visits and your agency’s don’t belong in the data. In the web stream details, click Configure tag settings → Show more → Define internal traffic → Create and enter the IP address. Then go to Data collection and modification → Data filters → Create Filter → Internal Traffic → Exclude. Run the filter in the Testing state first. Google warns that applying a data filter affects your data permanently.

2. Key events that match your Google Ads conversions

Important events in GA4 are called key events. From key events you create the conversions Google Ads uses to measure campaigns and steer bidding. So for your ad account, what matters is which events you turn into key events in the first place.

Which events they should be

A key event for Google Ads should mean a real enquiry or a real purchase, nothing more:

• Enquiries: Google recommends the event generate_lead for when someone submits a form or a request for information.
• Purchases: GA4 marks purchase as a key event by default.
• Not these: page views, scroll depth, clicks on “Contact”.

Be careful with form_submit from enhanced measurement. According to Google it fires when a user submits a form, any form. Newsletter sign-ups, call-back widgets and the contact form all end up in the same bucket. As an enquiry signal for Google Ads, that is too vague for me.

And one detail that is easy to miss in the help pages: if personalised ads are enabled in a linked Google Ads account, GA4 also marks add_to_cart, add_to_wishlist, begin_checkout, session_start, view_item, view_item_list and view_search_results as key events. In GA4 they do no harm. In Google Ads they must never end up as a primary conversion for bidding.

Build an enquiry event from a thank-you page, without code

If your form redirects to a thank-you page, you create the event directly in GA4. You need at least the Editor role.

1. Admin → Data display → Events → Create event → Create.
2. Under Custom event name, enter generate_lead.
3. Under Matching conditions, set event_name equals page_view and add a second condition: page_location contains your thank-you page address.
4. Click Create.
5. Once the event has arrived for the first time, mark it as a key event with the star icon on the Recent events tab under Events.

The original page_view event stays unchanged. Google explicitly advises against restricting page_view itself to one page, because you’d lose the data from every other page.

Value, currency and counting method

Three settings decide whether Google Ads can do anything with the key event:

• Value with a currency. If you set a value, Google’s event reference says the currency parameter in three-letter ISO format is required, so EUR. For enquiries, a fixed value derived from your closing rate is often enough.
• Counting method. “Once per event” is Google’s recommendation, “Once per session” is the legacy option. A change only applies to future key events.
• Patience. According to Google, a new key event can take up to 24 hours to appear in the standard reports. In the Realtime report you’ll see it within minutes.

A standard property allows up to 30 key events. For Google Ads you rarely need more than two or three.

3. Link, import and never count anything twice

The link

Without the link, no key event reaches Google Ads. According to Google, the import also needs auto-tagging switched on in Google Ads. How the link works, and why it also shows you visitor behaviour for every keyword, is covered in detail in Linking GA4 and Google Ads. Remarketing with GA4 audiences has its own guide: GA4 remarketing for Google Ads.

Import key events as conversions

According to Google, the import needs at least Marketer access in GA4. The route in GA4:

1. Open Advertising and, under the tools, select Conversion management.
2. Create a new conversion and click Next.
3. Select the Google Ads account.
4. Pick the events or key events to import and assign a category if prompted.
5. Click Next, review, then Save.

Google says creating conversions from key events isn’t available in every property. And there’s a trap in it: conversions based on Analytics key events are set up as secondary in Google Ads, so the same event isn’t counted twice for bidding. They then only count in “All conversions” until you set them to primary in Google Ads. For Analytics conversions you change primary or secondary only in Google Ads, not in GA4.

One thing I always check: your website must not lose the gclid click parameter, for example through a redirect that drops parameters. Otherwise Google can’t match the conversion to a click.

What you must not count twice

This is the part not to skip. Google Ads distinguishes:

• Primary actions show in the “Conversions” column and feed bidding when their goal is used for bidding.
• Secondary actions are for observation only and show in “All conversions”.

If the Google Ads tag measures the same enquiry as the imported GA4 key event, and both are primary, every enquiry counts twice. Smart Bidding then learns from doubled numbers, and your cost per enquiry looks half of what it really is. Pick one source per action and switch the other: Goals → under Conversions click Summary → Edit goal → in the “Conversion action optimization” section choose Secondary (observe only) → Save.

Two exceptions are worth knowing. If an action sits in a custom goal, Google’s help says it’s used for reporting and bidding whether it’s primary or secondary. And for enquiries, Google recommends counting One conversion in Google Ads, because usually only one enquiry per ad click is worth anything. Also make sure at the source that generate_lead fires only once per enquiry.

Don’t forget consent

In Germany, GA4 only fully sees visitors who consented. Anyone who declines is missing from the reports. With Consent Mode in the advanced implementation, GA4 can estimate those visitors’ behaviour, but only if the property reaches Google’s minimum volumes, such as 1,000 events a day with analytics consent denied for at least seven days. Which consent mode variant suits you and how to set the signals is in Consent Mode v2 setup. Do it before the import, not after.

The bottom line

• Create the property with the same time zone and currency as your Google Ads account, add a web stream, make sure the Google tag loads on every page.
• On day one: data retention to 14 months, internal traffic filtered in Testing first, then Active.
• Key events only for real enquiries and purchases. generate_lead rather than form_submit, values always with currency.
• Imported GA4 conversions start as secondary. Check in Google Ads what is really primary.
• One primary source per action: either the Google Ads tag or the GA4 import, never both.
• Consent mode is in place before the first conversion feeds into bidding.

GA4 is running, but you don’t trust the conversions in Google Ads? If you’re facing a specific decision, such as GA4 import or Google Ads tag as the primary source, the Clarity Session helps: from €390, a 60-minute video call with up to three links or documents reviewed first. Afterwards you know which source counts and what to switch in which order. If you want your tracking checked in full, the conversion tracking audit covers that, and having it set up for you is described under conversion tracking setup (in German). Whether the session fits your question is something you can check first in a free intro call. Book a free intro call.

FAQ

Do I need GA4 if Google Ads already counts conversions itself?

Not necessarily for bidding. The Google Ads tag measures conversions from Google Ads; GA4 measures every channel and shows you what visitors do between the click and the enquiry. For remarketing with GA4 audiences and for keyword analysis by behaviour, you need GA4 and the link.

What is the difference between a key event and a conversion?

A key event is an event you mark as important in GA4. A conversion is what you create from it for Google Ads, to measure campaigns and steer bidding. Not every key event has to become a conversion.

Why does GA4 show different numbers from Google Ads?

Both systems count by their own rules, for example in how they credit channels, in timing and in counting method. In Germany, consent comes on top: anyone who declines is fully or partly missing in GA4. A gap is normal. But if Google Ads shows almost exactly twice as many enquiries as actually reach your inbox, check for double counting first.

How long until data shows up?

According to Google, new key events appear in standard reports within 24 hours, and in the Realtime report within minutes. Allow some time for the import into Google Ads as well, and test with a real enquiry before you trust any number.