Tracking
Signups across domains
A visit on example.com and a signup on app.example.com are two sessions by default, because a browser keeps session storage per origin. The signup then shows up with no source: the referrer, campaign and landing page stayed on the first domain. This page is how to carry the session across, so the event on the second domain is read against the visit that started on the first.
Nothing on this page is needed when the site and the app share one origin. It is for a marketing site and an app, a shop and a checkout on another domain, or a site split across country domains.
Before you start
Both domains need the Clerion snippet with the same site id. On the app, auto-tracking can stay on or off: with data-auto-track="false" the app sends only the events you name, so its pages never count toward the site's traffic. See Script tag.
Subdomains: nothing to do
A link from example.com to app.example.com carries the session over on its own. When a visitor clicks a link to a sibling subdomain, the snippet adds clerion_sid to the link, and the snippet on the other side continues that session instead of starting one. There is nothing to add to the links.
Any custom event sent on the app then belongs to the session that began on the site:
window.clerion.trackEvent("signup_completed", { plan: "starter" });
The hand-off applies to links the visitor clicks. A redirect, a form action or a link built in JavaScript that navigates with location.href does not go through a click, so use linkTo for those.
A different domain: linkTo
When the two domains do not share a root, for example example.com and example-app.io, build the link with linkTo:
const href = window.clerion.linkTo("https://example-app.io/signup");
It returns the address with the current session attached. Use it wherever you build the link: a React href, a redirect, or a form submission that opens the other domain. The snippet on the other domain reads the parameter when it loads and continues the session.
A link built before the tracker exists has no session to attach; guard it, or set the href once window.clerion is there.
What you see
On Custom events, the event sent from the app counts with the source of the visit that led to it. Conversion insights and Revenue by source read the same session, so a purchase on the app is credited to the campaign or referrer that brought the visitor to the site. Over MCP, the conversion insights tool answers the same way.
Limits
| Limit | What it means |
|---|---|
| Same tab | The session lives in the tab. A link opened in a new tab carries the session in its address; a visitor who types the app's address into a new tab starts a fresh session. |
| 30 minutes | A session ends after 30 minutes without activity, on either domain. A signup after that is a new session with no source. |
| Click only | The automatic hand-off to a subdomain happens when a link is clicked. Redirects and script navigation need linkTo. |
| Two-label root | "Same site" is judged on the last two labels of the hostname, so shop.example.co.uk and example.co.uk do not match on their own. Use linkTo. |
The parameter is a session id only. It carries no personal data and nothing about the visitor's previous pages; those stay in the events already recorded on the first domain.