AnyTrack Identifiers
Understand every identifier AnyTrack uses to track and attribute conversions, from the Client ID and Click ID to refId, Property ID, and Tracking Group, plus the ad network click IDs AnyTrack collects and the fields that carry them across your marketing stack.
This page is the complete reference for the identifiers AnyTrack uses to connect a visitor, their actions, and the conversions they generate across your marketing stack.
If you want to understand how the Click ID stitches a customer journey together, see AnyTrack Click ID. If you want to send events without the Tracking Tag, see Server-Side Client ID.
Quick reference
Section titled “Quick reference”| Identifier | Parameter | What it identifies | Granularity |
|---|---|---|---|
| Client ID | cid | The visitor (anonymous) | One per visitor cookie |
| Page Click ID | AnyTrack('atclid') | The visitor, at one minute | Changes every minute (30 characters) |
| Click ID | click_id | One tracked event | One per tracked event (34 characters) |
| External ID | refId | An external alias you control | One per customer record |
| Property ID | {propertyid} | The tracked website | One per AnyTrack property |
| Tracking Group | tgid | An integration or group of links | One per integration |
Quick mnemonic: cid is who, the Page Click ID is who and which minute, click_id is which event, refId is your own name for them.
Core identifiers
Section titled “Core identifiers”These four identifiers carry the visitor and their actions through AnyTrack.
| Identifier | Parameter | Definition | Where it is generated |
|---|---|---|---|
| Client ID | cid | A cookie ID that anonymously identifies the visitor. A 14-character alphanumeric string. | Set as a first-party cookie by the Tracking Tag (two-year lifetime), or minted server-side via the collect endpoint. AnyTrack saves the Client ID server-side and restores it when a browser caps the cookie or the visitor deletes it. |
| Page Click ID | AnyTrack('atclid') | A 30-character ID: the Property ID, the Client ID, and 4 time characters for the current minute. It stays the same for one minute. It is not tied to one event. AnyTrack matches it to the latest event of the visitor. | The Tracking Tag computes it each time you run AnyTrack('atclid'). The Tag does not store it. |
| Click ID | click_id | A 34-character ID of one tracked event, such as the click on one link or the submit of one form: the Property ID, the Client ID, and an 8-character event ID. AnyTrack matches it to that exact event. This is the value that travels between platforms. | The Tracking Tag appends it per element through AutoTag. Server-side, you can send the Property ID joined to the cid ({propertyid}{cid}, 26 characters). AnyTrack matches that value to the visitor, not to one event. |
| External ID | refId | An external alias for a cid, such as an email, phone number, or your own customer ID. | You supply it when the click_id cannot reach a destination such as a CRM. |
Structural identifiers
Section titled “Structural identifiers”These identifiers describe your account setup rather than a single visitor.
| Identifier | Parameter | Definition |
|---|---|---|
| Property ID | {propertyid} | Identifies the property (website) being tracked. It forms the prefix of every Click ID. |
| Tracking Group | tgid | References an integration or a group of links so AutoTag knows which links and forms to append the Click ID to. Examples: typeform, ghl. |
How the Click ID is structured
Section titled “How the Click ID is structured”The AnyTrack Click ID is composed of three strings that let AnyTrack rebuild the visitor timeline:
| Property ID (12 characters) | Client ID (14 characters) | Event ID (8 characters) |
|---|---|---|
IBTO9lOfAMyb | rKiiB1U9YG91IF | js3Dv9AV |
The full value looks like IBTO9lOfAMybrKiiB1U9YG91IFjs3Dv9AV. The 8-character event ID has two parts: 4 time characters, then 4 random characters. The time characters are a base-62 encoding of the minute. It is an encoding, not encryption. The random characters make each event ID different, so a Click ID matches one exact event.
The Page Click ID is shorter. It is the Property ID, the Client ID, and the 4 time characters of the current minute: 30 characters. The first 30 characters of a Click ID equal the Page Click ID only when both are made in the same minute. In server-side setups, you can send the Property ID concatenated with the cid you generated: {propertyid}{cid}. That value has 26 characters, and AnyTrack matches it to the latest event of the visitor before the conversion.
The Page Click ID stays the same for one minute. Its 4 time characters change when the minute changes. The Property ID and the Client ID stay the same for the visitor. A different _atid value from one minute to the next is expected. AnyTrack identifies the visitor by the Client ID, so attribution does not change.
AnyTrack matches the value that you send by its length: 34 characters match one exact event, 30 characters match the latest event of the visitor, and 26 characters match the latest event of the visitor before the conversion. See Server-Side Client ID for the full rules.
Where identifiers are generated
Section titled “Where identifiers are generated”Client-side (Tracking Tag)
Section titled “Client-side (Tracking Tag)”When the Tracking Tag runs in the browser, it sets the Client ID in the _atcid cookie and appends a click_id to each trackable element through AutoTag. The command AnyTrack('atclid') returns the Page Click ID on request.
Server-side (collect endpoint)
Section titled “Server-side (collect endpoint)”When the Tracking Tag cannot run (Facebook Lead Ads, offline conversions, headless checkouts, or a contact created directly inside a CRM), AnyTrack creates the session server-side. You generate a 14-character cid, send a PageView to the collect endpoint, and identify later events with {propertyid}{cid}. AnyTrack matches that value to the latest event of the visitor before the conversion. See Server-Side Client ID for the full payload.
How the Click ID travels
Section titled “How the Click ID travels”A Click ID moves through four stages. A single platform can act at more than one stage.
- Generation — the Tag (client-side) or the collect endpoint (server-side) creates the identifier.
- Propagation — AutoTag appends the Click ID to links and embeds, a hidden form field or action URL carries it through the
--CLICK-ID--token, or an integration (or Zapier or Make) passes it along. - Landing — the destination stores the Click ID value in a field, such as a CRM contact property.
- Matching — the conversion returns to AnyTrack through a native integration event or a webhook, and AnyTrack matches it back to the original session by the
click_id, or by therefIdwhen theclick_idcould not travel.
For example, a Typeform embed receives the Click ID when the page loads (a destination), then returns the conversion on submit (a source).
Fields that carry the Click ID value
Section titled “Fields that carry the Click ID value”Each platform stores the value in its own field. These field names are not new identifiers. Most fields hold the 34-character Click ID. Some fields hold a shorter form: the LeadsHook atclid field holds 30 characters (the Page Click ID of that minute), and the HubSpot property holds 26 characters (the Property ID and the Client ID). AnyTrack accepts the 34-, 30- and 26-character forms. For the end-to-end external-form → CRM workflow, see Pass the Click ID from External Forms to Your CRM.
| Platform | Field | Naming |
|---|---|---|
| Typeform | at_click_id | Fixed by the integration |
| Unbounce | click_id | Fixed by the integration |
| Elementor | click_id | Fixed by the integration |
| Calendly | utm_term or sfid | Fixed by the integration |
| ClickFunnels | click_id | Fixed by the integration |
| LeadsHook | atclid | Fixed by the integration |
| GoHighLevel | Custom field shown as _atid, with the field key contact.atclid | Fixed by the integration |
| HubSpot | Contact property with the label AnyTrack Click ID and the internal name atclid | Fixed by the integration |
| LeadByte | c3 | Fixed by the integration |
| Custom integration (webhook) | click_id, clickid, click-id or click. Not atclid or _atid | Fixed by the integration |
| Generic HTML form | Any name you choose, carrying the --CLICK-ID-- token value | Free |
Ad platform identifiers
Section titled “Ad platform identifiers”Identifiers AnyTrack collects
Section titled “Identifiers AnyTrack collects”AnyTrack reads each ad platform click ID, plus the platform client-side identifiers when present (for example, the Meta fbp cookie and the Google Analytics client ID _ga). These belong to the ad platforms. They feed into the AnyTrack Click ID. They do not replace it.
| Click ID | Network |
|---|---|
gclid | Google Ads |
gbraid | Google Ads |
wbraid | Google Ads |
fbclid | Facebook Ads |
ttclid | TikTok Ads |
msclkid | Microsoft Ads |
oppref | ChatGPT Ads |
tblci | Taboola |
ob_click_id | Outbrain |
The identifier AnyTrack sends back
Section titled “The identifier AnyTrack sends back”AnyTrack sends the AnyTrack Client ID to some ad platforms as a matching identifier. On Facebook Ads, this identifier raises Event Match Quality. The path depends on the platform:
| Network | Path | AnyTrack Client ID sent as |
|---|---|---|
| Facebook Ads | Conversion API | external_id |
| TikTok Ads | Conversion API | external_id |
| ChatGPT Ads | Conversion API | external_ids_sha256 |
| Microsoft Ads | Conversion API | anonymousId |
| Google Ads | Google tag in the browser | user_id |
AnyTrack sends conversions to Google Ads through a server-side connection. This connection does not carry the AnyTrack Client ID. AnyTrack sends the Google client ID, the Google click ID, and hashed customer data.
AnyTrack does not send the AnyTrack Client ID to Taboola or Outbrain.
AnyTrack Identifiers FAQ
FAQ was last reviewed on 2026-11-13
What is the difference between the Client ID and the Click ID?
cid) is a cookie that identifies the visitor. The Click ID (click_id) identifies an action that visitor performed, and it is the value that travels between platforms. In server-side setups, you can send the Property ID joined to the cid ({propertyid}{cid}, 26 characters). AnyTrack matches it to the latest event of the visitor before the conversion.What is the difference between atclid and click_id?
AnyTrack('atclid') returns the Page Click ID: 30 characters (Property ID, Client ID and the current minute) that stay the same for one minute. The click_id is 34 characters: the Property ID, the Client ID and an 8-character event ID (4 time characters and 4 random characters). A Click ID matches one exact event. A Page Click ID matches the latest event of the visitor. The name atclid also appears on cross-domain links, where it carries the 34-character Click ID.Why is the _atid value different from one page to the next?
_atid URL parameter carries the Page Click ID. The Page Click ID contains the current minute, so its last 4 characters change when the minute changes. The Property ID and the Client ID stay the same. Two pages that load in the same minute show the same value. AnyTrack identifies the visitor by the Client ID, so a different value on the next page is normal and does not affect attribution.When does AnyTrack generate a Click ID server-side?
When should I use refId instead of the click_id?
refId when the click_id cannot be passed to a destination such as a CRM. It aliases the visitor by an external value you control, like an email or your own customer ID, so later events identified by that value match back to the same visitor. See External ID as Click ID.What identifier does AnyTrack send to Meta and Google for matching?
external_id through Conversion API. ChatGPT Ads receives it as external_ids_sha256, and Microsoft Ads as anonymousId. On Facebook Ads, this identifier raises Event Match Quality. On Google Ads, the Tracking Tag sets the AnyTrack Client ID as user_id on the Google tag in the browser. The server-side connection to Google Ads carries the Google client ID, the Google click ID, and hashed customer data when AnyTrack has them.