# Identity

> Keep one person as one person across your domains in ClickClacks: carrying identity between listed domains, the carry-over measure and its 80% threshold, and how identify and merges fit in.

- Canonical URL: https://clickclacks.io/docs/guides/identity
- Section: Product guides
- Last updated: 2026-09-26

When someone moves from your marketing site to your app on another domain, the browser treats them as a stranger. Identity keeps them as the same person, and shows you how well that is working.

## Why it matters {#why}

Say your site is `acme.com` and your app is `acme.app`. Without help, a visitor who clicks _Start free trial_ becomes a new, anonymous [person](https://clickclacks.io/docs/glossary.md#term-person) on the app. Your funnel from pricing to sign-up then shows a drop that never happened, and your referrer and UTM reports lose the campaign that brought them.

## Carry identity between domains {#carry}

1. Open **Sources** › **Identity** (also under Settings).
2. Check that every domain you own is listed. Click **Add a domain** for any that are missing.
3. Turn on **Carry identity between these domains**.

Links between listed domains are then tagged with a short `_ccid` parameter, so the next page knows who arrived. You don’t need to change your markup. Changes apply to future visits, not to people already seen. How the tracker handles domains is covered in [Domains and identity](https://clickclacks.io/docs/domains.md).

## Is it working? {#measure}

The **Is it working** card shows **Kept the same ID across a hop**: of the people who followed a link from one listed domain to another and arrived within 30 minutes, the share whose first event already carried an ID we knew. It covers the last 30 days, with a row for each hop, such as _acme.com → acme.app_.

- **80% or more** is _healthy_.
- **Below 80%** is flagged as _needs attention_.

The same number appears at the top of funnels and experiments that span two sources, so you know whether to trust the handover. It measures the raw hand-off only. Manual merges don’t change it.

## Identify, devices and merges {#identify}

- **Carrying** joins one visit across domains, while the person is still anonymous.
- **Identify** joins everything once you know who they are. The first browser to identify with a user ID becomes the person’s main record. Later browsers that identify with the same ID are linked to it automatically, with their earlier history.
- **Merge** joins two records by hand. See [People and profiles](https://clickclacks.io/docs/guides/people.md#merge).

## Tips and gotchas {#tips}

- **Only listed domains carry.** A new domain needs adding here, or in the Add source dialog, before links to it are tagged.
- **Redirects can drop the parameter.** If a hop is below 80%, check that redirects between your domains keep the query string.
- **Subdomains** of the same site, such as `www.acme.com` and `app.acme.com`, are listed too, marked as subdomains.

## Recipes {#recipes}

### Follow visitors from our site into our app.

1. Make sure the site and the app are both sources in the same project.
2. In **Identity**, turn on **Carry identity between these domains**.
3. A day later, check **Kept the same ID across a hop** for the site → app hop.

At 80% or more, funnels from the pricing page to sign-up count the same people end to end.

### A hop reads 42%. Why?

1. Check that both domains are listed and receiving.
2. Open **Realtime**, then click a link from your site to your app yourself. Open both pageviews in **Event details**: they should name the same person.
3. If they don’t, look for a redirect between the two domains that drops the query string, where the `_ccid` tag travels. The tracker removes the tag from the address bar once it has read it.

## Related {#related}

- [Domains and identity](https://clickclacks.io/docs/domains.md): The tracker side of cross-domain identity.
- [Sources](https://clickclacks.io/docs/guides/sources.md)
- [Funnels](https://clickclacks.io/docs/guides/funnels.md): Cross-domain funnels depend on this.
- [People and profiles](https://clickclacks.io/docs/guides/people.md)