Identity Resolution
Understand how AnyTrack identity resolution links the sessions a person creates across devices, domains, and time using first-party data, click IDs, and stored UTM parameters, so conversions stay attributed to the original campaign even after UTM values leave the URL.
A visitor clicks your ad, lands on your site, and leaves. Three days later they come back on their phone, type your address directly, and buy. How does that purchase still get credited to the ad that started it? That job is called identity resolution, and AnyTrack does it automatically. You do not configure it or turn it on.
The short answer: AnyTrack collects a set of durable signals the moment a visitor arrives, stores them as first-party data, and then matches every later session and conversion back to the same visitor profile, even when the original UTM parameters are long gone from the URL.
What identity resolution is
Section titled “What identity resolution is”Identity resolution is the process of matching incoming sessions and conversions to the correct visitor profile. It answers a single question: are these two interactions the same person, and which campaign first brought them in?
UTM parameters only appear on the URL at one moment, the landing from a campaign. They then drop out of the address bar as the visitor browses, and they are usually absent entirely when that person returns directly, from email, or on another device. Without a way to reconnect those visits, every return would look like brand-new, unattributed traffic. Identity resolution is what stitches them together.
How AnyTrack resolves identity
Section titled “How AnyTrack resolves identity”AnyTrack does not rely on one identifier. It resolves identity server-side and from browser signals, combining several layers so that a match survives cleared parameters, new sessions, and device switches. The main signals are:
- The AnyTrack first-party cookie (
_atcid) — set on your own domain with a two-year lifetime. It recognizes the same browser across sessions over time, and the companion_atutmcookie remembers the campaign parameters the visitor first arrived with. See First-Party Data. - The AnyTrack Click ID (
click_id) — ties an outbound click to the conversion it eventually produces, even when that conversion happens on a different domain. This is also what AutoTag carries across domains and what affiliate postbacks match on. - Ad platform cookies — signals like
_fbp(Meta) and_ga(Google) connect a conversion back to the ad click that opened the session. - Hashed customer data — when an email, phone, or name is collected through a webhook, CRM, or form, AnyTrack uses it to link a returning visitor to their earlier interactions, including across devices. This data is hashed with SHA-256 before it is ever sent to an ad platform.
Together these signals let AnyTrack carry the first campaign touch forward through the whole journey. The data orchestration walkthrough shows the same matching happening step by step across a real click-to-conversion path.
Why attribution survives UTMs leaving the URL
Section titled “Why attribution survives UTMs leaving the URL”This is the design decision that surprises people. AnyTrack tracks every session and every conversion whether or not UTM parameters are present. Tracking does not require them.
What UTMs do is supply the campaign label. Identity resolution preserves that label by attaching it to the visitor profile on the first visit, then reattaching the profile to each later session. So a conversion that happens days later, on a UTM-free direct visit, still rolls up to the campaign that earned the first click.
The one thing identity resolution cannot invent is a campaign that was never recorded. If no visit in the journey ever carried a UTM, AnyTrack still tracks the session and the conversion, but there is no source to attribute it to in your reports. That is why campaign URLs need UTM parameters even though the rest of the journey does not. See UTM Parameters for how those values are structured.
What identity resolution can and cannot do
Section titled “What identity resolution can and cannot do”Identity resolution is strongest when it has durable, first-party signals to work with. It is not magic, and a few real-world limits apply:
- Cross-session, same browser is the most reliable case. The
_atcidcookie holds for two years unless the visitor clears it. - Cross-domain works because the
click_idtravels with the visitor between your site and a merchant or affiliate domain. - Cross-device depends on a shared identifier. AnyTrack can link two devices when the same person provides a matchable signal on both, such as the same email at checkout. With only anonymous browsing on a second device, there is nothing to match on.
- Privacy controls matter. Cleared cookies, private browsing, and aggressive blockers reduce the signals available, which is one reason server-side collection is valuable. See Server-Side Tracking.
How identity resolution shapes your results
Section titled “How identity resolution shapes your results”Identity resolution feeds two outcomes you can see in the product:
| Outcome | What identity resolution contributes |
|---|---|
| Attribution reports | Keeps the first campaign touch attached to later sessions, so the Campaign Report credits the right source even after UTMs disappear. |
| Ad platform match rates | More matched signals raise Event Match Quality on Meta and equivalent match rates elsewhere, so platforms attribute and optimize on more of your conversions. |
To protect the first-touch campaign data that identity resolution relies on, configure Ignored Sources so intermediaries such as PayPal or Mailchimp do not overwrite your stored UTM values mid-journey.
Identity Resolution FAQ
FAQ was last reviewed on 2026-07-16
Do I need to set up identity resolution?
How does AnyTrack attribute a conversion after the UTM parameters are gone?
_atcid cookie, the AnyTrack click_id, ad platform cookies, and hashed customer data. The original campaign stays attached to that profile, so a later UTM-free visit still credits the right campaign.