The essentials
- Automatic: GA4's enhanced measurement sends a
clickevent for any link to another domain, with no code. - The useful parameter:
link_url, to be registered as a custom dimension so you can see the destinations in your reports. - Special cases: subdomains and cross-domain domains (treated as internal), and
tel:andmailto:links (not covered — handle them in Tag Manager). - How to use it: measuring a partnership, a marketplace or an external booking tool, and turning it into a key event when it is a conversion.
An outbound link is a link leading to another site: a marketplace where you sell, an external booking tool, a partner, a social network, a document hosted elsewhere. For many sites, those clicks are conversions in their own right: the tradesperson whose quotes go through a platform, the restaurant whose bookings happen on a third-party service. GA4 measures them with no configuration, provided you know where to read them.
What GA4 collects automatically
Enhanced measurement , switched on by default on a web stream, sends aevent every time a visitor clicks a link whose domain differs from the current one. That event carries several parameters: click Parameter
| Content | Example | The full destination URL |
|---|---|---|
link_url | https://www.marketplace.com/shop/xyz | The destination domain |
link_domain | marketplace.com | The link's CSS classes |
link_classes | btn btn-primary | The link's HTML identifier |
link_id | cta-booking | Always "true" for an outbound link |
outbound | true | Check that the "Outbound clicks" option is ticked in |
Admin > Data streams > Enhanced measurement . TheEngagement > Events report then shows the number of events, but not their destinations: for that you need a custom dimension. How clickGA4 events work in general is covered in our guide. Admin > Data display > Custom definitions > Create custom dimension
Seeing the destinations: creating the link_url dimension
- Name: "Outbound link URL"; scope: Event; event parameter:.
- . Do the same for
link_urlWait 24 to 48 hours. Inlink_domain. - , click report then shows the number of, or build an exploration with the "Outbound link URL" dimension and the "Event count" metric.
clickData from before you created the dimension can't be used: create it as soon as you install GA4. The limits (50 custom dimensions) and the principle are explained in
GA4 custom dimensions and metrics If the click through to your marketplace or your booking tool is a conversion, create a dedicated event:.
Turning an outbound click into a key event
Admin > Events > Create event , with the condition "event name equals click AND link_domain contains booking-partner.com", and a new name. Then mark it as a clic_reservationkey event with an estimated value. You will then know which channels bring the visitors who book, even though the booking itself happens elsewhere. Subdomains and linked domains
The cases enhanced measurement doesn't cover
- : a link to from
boutique.votresite.fris not treated as outbound. The same goes for domains declared in your cross-domain configuration. That is deliberate: it is the same site.www.votresite.frLinks - : these aren't outbound links as far as GA4 is concerned. Create triggers in
tel:andmailto:Google Tag Manager (Click URL starts with tel: or mailto:) with events.clic_telephoneandclic_email. - JavaScript buttons that open an external site without an
<a href>tag: invisible to enhanced measurement, and to be instrumented through Tag Manager. - Files (PDF, XLS): covered by the
file_downloadevent, not byclick.
id (id="cta-reserver"). The link_id parameter then becomes a simple way to tell the button at the top of the page from the one at the bottom, without relying on URLs.
Reading and using the results
Three questions outbound clicks answer:
- Which external links capture your visitors? An exploration on "Outbound link URL", sorted by event count. If a link to a social network comes top, your visitors are leaving before converting: move it to the footer.
- Which pages send people to your partners? Add the "Page path" dimension: you identify the content that triggers the action.
- Which channels bring the visitors who click? Once the key event is created, the Traffic acquisition report answers directly. These are the classic conversion KPIs , applied to an off-site conversion.
A concrete example
A restaurant uses an external booking service. Before configuration, GA4 showed 2,400 monthly sessions and no conversions. After creating the link_domain dimension and the clic_reservationkey event, it turned out that 190 visitors a month click through to book, 60% of them arriving from the Google Business Profile listing (thanks to UTMs on the listing) and only 8% from Instagram posts. The social advertising budget was redirected towards optimising the listing.
How GreenRed helps
Rather than juggling several tools, GreenRed's Traffic module brings these metrics together in a single dashboard, compares them over time and tells you which actions come first. You can try it free, with no card, from the Pricing.
Frequently asked questions
Does GA4 track outbound clicks automatically?
Yes, if enhanced measurement is switched on with the "Outbound clicks" option (the default on a web stream). GA4 then sends a click event with the destination URL and domain for any link to another domain. You do, however, need to create a custom dimension on link_url or link_domain to see the destinations in your reports.
Why aren't clicks to my subdomain counted as outbound?
GA4 treats subdomains of the current domain as part of the same site, along with any domains declared in cross-domain measurement. Those clicks are internal navigation, measured by page views. If you want to count them anyway, create a custom event in Tag Manager.
Can enhanced measurement track clicks on a phone number?
No. tel: and mailto: links aren't treated as outbound links. In Google Tag Manager, create a "Click - Just links" trigger on URLs starting with tel: (or mailto:) and a GA4 event tag named phone_click. Then mark it as a key event.
How do I turn an outbound click into a conversion in GA4?
Create an event from click with a condition on link_domain (Admin > Events > Create event), give it an explicit name such as booking_click, then mark it as a key event. You will then be able to see which channels generate those clicks in your acquisition reports.