Why click IDs exist
When you click an ad, the platform needs to know, eventually, whether that click led to a purchase. Click IDs are the mechanism. The platform attaches a unique parameter to the URL, your site stores it (cookie, localStorage, or server-side), and when the user converts, you ship the click ID back so the platform can match the conversion to the original click.
This is what powers ROAS reporting in every major ad platform. Without click IDs, the platform only sees its own pixel fire at the conversion, it has no way to know which of its impressions led to it.
Common click IDs
| Platform | Parameter | Notes |
|---|---|---|
| Google Ads | gclid (or gbraid/wbraid for iOS) | Auto-tagging adds it. gbraid/wbraid are the iOS App Tracking Transparency variants |
| Meta | fbclid | Added by Meta to outbound clicks. Persists in the URL |
| TikTok | ttclid | Added when TikTok Pixel is installed |
| Microsoft (Bing) | msclkid | Equivalent to gclid for Microsoft Ads |
li_fat_id | First-party variant of LinkedIn Insight Tag identifier |
These are all distinct from UTM parameters, UTMs describe the source qualitatively. Click IDs identify the specific click event.
How to handle click IDs correctly
Three steps:
- Capture on landing. Your site reads the click ID from the URL on first arrival.
- Persist. Store it in a first-party cookie or in your CRM / session record. It needs to be available when the conversion fires, which could be days later.
- Send back on conversion. When a purchase or other tracked event happens, include the click ID in the event payload to Meta CAPI, Google Enhanced Conversions, TikTok Events API, etc.
Server-side tracking makes this dramatically more reliable: the click ID lives in your backend instead of a browser cookie that ITP might delete.
Common mistakes
- Storing click IDs only in third-party cookies. Lost as soon as the browser strips them.
- Forgetting to include the click ID in CAPI events. Without it, the platform can match the conversion only by hashed email or IP, much weaker signal.
- Stripping click IDs on redirect. If your tag manager or analytics tool replaces the URL, the click ID disappears before your code can save it.
FAQ about Click ID
What is a click ID?
A click ID is a unique identifier appended to a URL when a user clicks an ad. It lets the ad platform recognise the resulting conversion as coming from that specific click. Examples: gclid (Google), fbclid (Meta), ttclid (TikTok).
Why does my click ID disappear after redirect?
Some redirects, tag managers, or analytics tools strip URL parameters. Capture the click ID on first arrival and persist it (cookie, server-side session) before any redirects can drop it.
Should I send the click ID with my CAPI events?
Yes. Including the click ID in CAPI events gives the platform the strongest possible signal to match the conversion to the original click. Without it, the platform falls back to weaker matching like hashed email or IP.