What a gclid Is
A gclid is the click ID Google Ads creates for every ad click when auto-tagging is on. It appears in the landing page URL as a parameter named gclid with a long, unique value. Google stores the details of that click, including campaign, ad group, keyword, device and time, against the value.
Anything that later sends the gclid back to Google, or to an attribution system that understands it, can link a conversion to that exact click. That makes the gclid one of the main deterministic signals for Google traffic on the web and in web-to-app journeys.
How Auto-tagging Works
Auto-tagging is an account setting in Google Ads. When it is on, Google appends the gclid to the final URL of every click on Search, Display, YouTube and other ad formats that send users to a page. You do not add it to links yourself, and it should not be added manually.
Most problems with gclids come from what happens next. A redirect that drops query parameters, a landing page that rewrites the URL, or a consent banner that blocks storing the value will all lose the gclid. Test the full click path from ad to landing page to conversion before relying on it.
gclid, gbraid and wbraid
Apple's App Tracking Transparency rules limit click-level tracking across apps and websites on iOS. In response, Google introduced two privacy-preserving parameters for some iOS traffic:
- gbraid for clicks that move between web and app, such as an ad on the web that leads to an app conversion.
- wbraid for web-to-web conversions on iOS where a gclid cannot be used.
Both identify a group of clicks rather than a single one, and Google uses them for aggregated conversion measurement. Systems that accept gclid usually accept gbraid and wbraid in the same places, such as offline conversion import.
How MMPs Use the gclid
For app growth teams, the gclid matters in three places:
- Web-to-app journeys. A user clicks a Google ad, lands on the web, then installs the app. If the web page keeps the gclid and passes it into the app store link or the install flow, the install can be matched to the click deterministically.
- Play Store referrer. A gclid passed into the Play Store referrer reaches the app on first open through the Google Play Install Referrer.
- Conversion import. Revenue or sign-ups that happen later can be sent back to Google against the gclid so bidding optimizes toward real value.
For Google App campaigns, Google acts as a self-attributing network: it decides which installs it drove and shares that with linked analytics providers. The MMP reads that attribution rather than looking for a gclid on a link.
Linkrunner reads ad click IDs such as gclid and fbclid as part of its deterministic matching, before any IP and user-agent fallback. Google Ads is linked to Linkrunner as a third-party app analytics provider, with event mapping to conversion actions and automatic campaign and spend sync. See Google and Meta ads for the setup and web-to-app for web journeys.
Privacy and Consent
A gclid is an ad click identifier, not a personal identifier on its own, but it is still covered by consent rules in many regions. In the EEA, the UK and Switzerland, Google's consent requirements under the Digital Markets Act decide what can be sent back to Google. Consent signals need to travel with conversions so Google can treat them correctly. Linkrunner passes Google consent signals for the DMA.
Browsers also limit click IDs. Some private browsing modes remove known tracking parameters from links, which lowers the share of conversions with a gclid. Expect some gap between clicks and gclid-matched conversions, and avoid treating it as a tracking bug without checking.
Quick Checklist
- Auto-tagging is on in Google Ads.
- Landing pages and redirects keep all query parameters.
- The gclid is stored with the visitor and passed into store links or install flows.
- Conversions sent back to Google include the gclid and consent state.