atclid is a name, not one value. It is a URL query parameter, a Tag command and a field name, and the value behind it differs:
Where the name atclid appears | What it holds | Length |
|---|---|---|
The command AnyTrack('atclid') | The Page Click ID | 30 characters |
The atclid URL parameter on cross-domain links | The Click ID | 34 characters |
The atclid field of a LeadsHook form | The first 30 characters of the Click ID, which equal the Page Click ID of that minute | 30 characters |
The HubSpot property with the internal name atclid, and the GoHighLevel custom field with the field key contact.atclid | The Property ID plus the Client ID, written by the HubSpot form or written back by AnyTrack | 26 characters |
A GoHighLevel form also fills the contact.atclid custom field. The form builder takes the value from the _atid parameter in the page URL, and _atid carries the 30-character Page Click ID.
Where the atclid parameter is used
Section titled “Where the atclid parameter is used”- Cross-domain links, when Sync Conversions is OFF or has no event names selected. Links pointing at another domain you own carry
atclidwith the 34-character Click ID. When Sync Conversions is ON, they carry atrefid instead, with the same Click ID, and the conversion recorded on the destination returns to the source Property. - Email marketing. If you collected the Click ID value at form submission and stored it against the subscriber, append it to the links in your emails:
propertyURL.foo/?atclid=<value>. When the subscriber lands on a page where the Tracking Tag loads, the Tag reads the Property ID in the value. If it matches the Property of the page, the Tag takes the 14 characters after it as the visitor’s Client ID. AnyTrack then resolves the visitor’s identity from earlier sessions and conversions, so later conversions attribute back to the original ad click. - SamCart. Links from your landing page into the SamCart checkout are autotagged with
atclid=<value>, so the completed order carries the Click ID back to AnyTrack.
What atclid is not
Section titled “What atclid is not”atclid is not the identifier itself. See Page Click ID for the 30-character value that AnyTrack('atclid') returns, and Click ID for the 34-character value of one tracked event. The atclid parameter is also not the parameter for same-page click-ID collection. That is _atid, which the Tracking Tag writes into the current page URL.
Frequently asked questions
FAQ was last reviewed on 2026-11-08
When do cross-domain links carry atclid instead of atrefid?
When Sync Conversions is OFF, or when no event names are selected, the links carry atclid. When Sync Conversions is ON with at least one event name, they carry atrefid, and the conversion recorded on the destination is sent back to the source Property. Both parameters carry the 34-character Click ID.
Can I add atclid to my email links?
Yes. Store the Click ID value against the subscriber when the form is submitted, then append it to your email links as propertyURL.foo/?atclid=. When the subscriber lands on a page carrying the Tracking Tag, the Tag reads the Property ID in the value. If it matches the Property of the page, the Tag takes the 14 characters after it as the visitor's Client ID. AnyTrack then resolves the visitor's identity from earlier sessions and conversions.
I see atclid on links to my SamCart checkout. Is that correct?
Yes. AutoTag appends atclid to links from your landing page into the SamCart checkout, so the completed order carries the Click ID back to AnyTrack.