What a Click ID Is
A click ID is a one-time identifier attached to a single ad click. When a user taps an ad, the network or the attribution platform creates the ID, stores the details of the click against it, and passes it along in the URL. If the same ID later arrives with an install or a purchase, that conversion can be credited to the exact click, campaign, ad set and creative.
Click IDs are the backbone of deterministic attribution. They replace guesswork with a direct key: this install came from this click.
Common Click IDs
Most large ad platforms create their own click ID and append it to the destination URL:
- gclid, plus gbraid and wbraid on iOS, for Google Ads. See gclid.
- fbclid for Meta, on clicks from Facebook and Instagram. See fbclid.
- ttclid for TikTok.
- ScCid for Snapchat.
- li_fat_id for LinkedIn.
- msclkid for Microsoft Advertising.
- rdt_cid for Reddit.
ChatGPT Ads uses its own click ID, called oppref, which an MMP sends back through the OpenAI Conversions API.
MMPs add their own layer. When a user taps an attribution link, the MMP records the click with its own ID and any network click ID that came with it, then redirects to the store or the app.
How Click IDs Travel to the App
The hard part of mobile attribution is getting the click ID from the ad to the first app open, across a store visit and an install.
On Android, the click ID can ride in the Play Store referrer. The app reads it through the Google Play Install Referrer on first open, and the MMP matches it to the click record. This is exact and does not depend on device IDs or consent.
On iOS, the App Store does not pass a referrer to the app. Click IDs reach the app through deferred deep linking, web-to-app flows that hand off a stored ID, device IDs where the user allowed tracking, or Apple's own frameworks for Apple Ads and SKAdNetwork.
On the web, the click ID sits in the landing page URL. Sites store it in a first-party cookie, then send it back with conversions or into the app install flow.
Click IDs in Linkrunner
Linkrunner matches installs deterministically first: the Google Play Install Referrer, ad click IDs such as gclid and fbclid, device IDs where the user allows it, and Apple AdServices for Apple Ads. It falls back to IP and user-agent matching only when no deterministic signal exists. Reddit click IDs, the ChatGPT Ads oppref click ID and the click IDs captured by the Web SDK all feed the same matching. See mobile attribution for how the matching order works.
For affiliate and S2S partners, Linkrunner postback templates support 30 macros, including the partner's own click ID, and accept AppsFlyer-style parameter names, so partners can receive their click ID back with each install postback.
Why Click IDs Go Missing
- A redirect between the ad and the landing page drops query parameters.
- The landing page rewrites the URL before scripts store the ID.
- Browser privacy features remove known click ID parameters in some contexts.
- The user switches from an in-app browser to the default browser and loses the original URL.
- The store link on the landing page does not pass the ID forward.
Each of these turns a deterministic match into an estimate, or into an organic install. Testing the full path from ad to first open on real devices finds most of them quickly.
Click IDs and Fraud
Because a click ID only proves a click happened, fraud targets clicks. Click spamming fires large numbers of clicks hoping to catch organic installs, and click injection fires a click just before an install completes. Fraud checks therefore look at click-to-install time, click volume per device or IP, and referrer timestamps, not only whether a click ID matched. Linkrunner's fraud protection includes templates for click injection and click flooding.