Domains & subdomains

Your domains list — set on the Setup page under Your website — is the set of websites we count visitors on. Events from anywhere else are ignored, so your numbers stay clean. If someone copies your snippet onto another site, by accident or on purpose, those visits are rejected as coming from an unverified domain and never touch your reports.

Subdomains are automatic

Adding yourdomain.com covers every subdomain: www.yourdomain.com, app.yourdomain.com, docs.yourdomain.com, all of them.

A visitor who clicks an ad to your marketing site and signs up at app.yourdomain.com is one visitor, automatically. Their token is stored at the broadest domain you've verified, so every subdomain reads the same identity. There is nothing to configure and no cross-subdomain setup step — this is the most common SaaS layout, and it works out of the box.

Separate websites

Only add a second domain if you run a genuinely separate website — like getproduct.com next to product.io.

Browsers don't share cookies between separate domains, so the pixel carries the visitor across the hop itself. When a visitor clicks a link (or submits a form) pointing from one of your verified domains to another, the pixel adds a one-time ar_token parameter at the moment of the click. On arrival, the pixel on the destination picks it up and the visitor continues as the same person.

Three behaviors worth knowing, because they're deliberate:

• An existing visitor is never overwritten. The handoff token is adopted only when the destination browser has no identity yet. A crafted link with someone else's token can't hijack or merge a real visitor.
• The parameter doesn't linger. ar_token is removed from the address bar immediately after it's read.
• Every way of clicking is covered. Normal clicks, middle-clicks, right-click → open in new tab, and cross-domain form posts all carry the token.

What you don't need to add

• Subdomains. Covered by the parent domain.
• Localhost or staging. Dev traffic is accepted and labeled as local traffic on the Events page — see Confirm it's live.