atclid is a URL query parameter. Its value is an AnyTrack Click ID. The Click ID is the generated value; atclid is one of the names that value travels under, in the same way as _atid and atrefid.
Where atclid is used
Section titled “Where atclid is used”- Cross-domain links, when Sync Conversions is OFF. Links pointing at another domain you own carry
atclid. When Sync Conversions is ON, they carry atrefid instead, 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, AnyTrack reads the value and 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 page-session value and Click ID for the 34-character element value. It is also not the parameter for same-page click-ID collection: that is _atid, which the Tracking Tag appends to the current page URL.
Frequently asked questions
FAQ was last reviewed on 2026-08-13
When do cross-domain links carry atclid instead of atrefid?
When Sync Conversions is OFF the links carry atclid. When Sync Conversions is ON, they carry atrefid, and the conversion recorded on the destination is sent back to the source Property.
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, AnyTrack reads the value and 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.