Google Ads Tracking: What Is GCLID, and Why Does It Go Missing Before the Conversion?

What is GCLID?

The short answer to "what is GCLID" is that a GCLID, short for Google Click Identifier, is the URL parameter that Google Ads auto-tagging adds to your landing page URL when someone clicks an ad. Google's help centre says the parameter "identifies the campaign along with other attributes of the click associated with the ad for ad tracking and campaign attribution." If you run Google Ads, keep auto-tagging on and make sure the GCLID reaches the page where your conversion tag fires.

The GCLID is not readable on its own. It is an opaque string that only Google's systems can decode back into the campaign, ad group, keyword and click it came from. That is the difference from a UTM tag such as utm_source=google, which any analytics tool can read in plain text.

How does auto-tagging add the GCLID?

Auto-tagging adds the GCLID to the URL at the moment of the click, so the landing page receives it as a query parameter. Google's example: "if someone clicks on your ad for www.example.com, the final URL will look like www.example.com/?gclid=123xyz."

Three details from Google's auto-tagging documentation matter in practice:

• It is on by default. "Auto-tagging is turned on by default for new accounts," and it switches on automatically when you create a new conversion action, unless you use cross-account conversion tracking.
• It is stored in a first-party cookie. With auto-tagging on and a Google Analytics tag on the site, "the GCLID is stored in a new Google Analytics cookie on your site's domain."
• One GCLID can cover several clicks. "Sometimes the GCLID is created at the time of an impression, rather than a click. In those cases, if a user clicks the same ad again, the same GCLID will be used."

To turn it on or off, go to Admin, then Account settings, then Auto-tagging, and check or uncheck "Tag the URL that people click through from my ad."

What is the GCLID used for?

Google Ads uses the GCLID to join a click to what happened after it: a conversion on your site, a session in Google Analytics or a sale recorded in your CRM. Google calls auto-tagging "a required feature" for conversion tracking.

Job	What the GCLID does	Source
Website conversion tracking	Links the conversion tag's hit to the ad click	Google says the GCLID is "required for Google Ads website conversion tracking"
Google Analytics linking	Imports Google Ads campaign and cost data into Analytics reports	Google Ads auto-tagging help page
Offline conversion import	Matches a CRM sale back to the click that created the lead	Google Ads offline conversion setup guide
Browser coverage	Keeps conversion tracking working in browsers that require auto-tagging	Google: "Some browsers require auto-tagging to track conversions."

GA4 also gives the GCLID priority over your own tags. Google's auto-tagging page states that "in Google Analytics 4 (GA4), auto-tagging is prioritized over manual tagging due to the absence of an override option," so a GA4 property reads the campaign from the GCLID even when the URL also carries UTM tags.

How do you capture a GCLID for offline conversions?

You capture a GCLID for offline conversions by saving it with the lead when the form is submitted, then uploading it with the sale later. Google's setup guide lays out the steps:

1. Add a hidden form field. Google says "You will need to modify each form submission page to add a hidden form field for the GCLID."
2. Store the value between pages. Update every page to capture the GCLID from the URL and keep it "via cookie or local storage." Google's suggested script sets a 90-day expiry on the stored value.
3. Save it in your CRM. Modify the backend so it can "store the GCLID along with the prospect's information."
4. Keep it exactly as received. "The GCLID is case sensitive, so make sure you're uploading it correctly."
5. Upload the conversion. Import each sale with its GCLID, conversion name and time. For scheduled imports from Google Cloud Storage, Amazon S3, HTTP, SFTP and Google Sheets, Google Ads Data Manager "imports conversions from 90 days ago in every run."

Google now points new setups at enhanced conversions for leads, which adds hashed email or phone data to the upload, but the GCLID column stays: "You need to send the GCLID with enhanced conversions for leads."

From ad click to offline conversion

Ad click

GCLID in landing page URL

Hidden form field

Cookie or local storage, 90-day expiry

CRM record

Offline upload

Why does the GCLID go missing?

The GCLID goes missing when anything between the ad click and the conversion tag drops the query string. Each gap below breaks the join between click and conversion:

• Redirects. Google warns: "If your website uses redirects, it's also important to make sure the GCLID is passed to the final landing page in order to track conversions." A short link, a tracking redirect or a country picker that rebuilds the URL without its query string loses the GCLID.
• Sites that reject unknown parameters. "A small percentage of websites don't allow arbitrary URL parameters and serve an error page when auto-tagging is turned on."
• Safari's Link Tracking Protection. Apple removes tracking information "from the links users share in Messages and Mail" and "from links in Safari Private Browsing." WebKit says Safari "removes a subset of query parameters that have been identified as being used for pervasive cross-site tracking granular to users or clicks," while parameters "only used for campaign attribution" pass through. Apple does not publish the list, so test your own ad URL in a Private Browsing window.
• Short cookie lifetimes. WebKit's tracking prevention "caps the expiry of cookies created in JavaScript on the landing webpage to 24 hours" when it detects click IDs in the link. In that case a GCLID kept in a JavaScript cookie is gone before a Safari buyer who returns two days later converts.
• iOS app traffic. Google Ads uses separate identifiers for iOS: GBRAID "is present when a user clicks on an ad on the web and is directed to your iOS app," and WBRAID "is present when a user clicks on an ad in an iOS app and is directed to your webpage."

When a GCLID is stripped and the ad has no UTM tags either, GA4 has only a Google referrer to go on and cannot tell the visit came from an ad. Tracking paid ads in cookieless analytics covers the setup that avoids that.

How is a GCLID different from UTM parameters?

A GCLID identifies one ad click for Google's systems, and UTM parameters label the campaign in plain text for any analytics tool. Most teams need both.

	GCLID	UTM parameters
Added by	Google Ads auto-tagging	You, in the ad's final URL
Identifies	A single click and its attributes	A campaign, source and medium
Readable by	Google Ads and Google Analytics	Any analytics tool
Safari Link Tracking Protection	Click-level parameters are its target, and Apple does not publish the list	Campaign-only parameters pass through
Needed for	Conversion tracking, offline imports, cost data	Campaign reports outside Google

The practical rule: keep auto-tagging on for Google's own measurement, and add UTM tags to your ad URLs so every other tool sees the campaign too. Keep the values consistent with your UTM tagging naming sheet, and read what cross-site tracking is for why browsers treat the two differently. Flowsery's UTM campaign tracking collects all five UTM parameters automatically the moment a visitor lands and ties revenue to each campaign, so UTM-tagged Google Ads show up by campaign, with the payments they drove, next to your other channels.

Frequently asked questions

What does GCLID stand for?

GCLID stands for Google Click Identifier, or Google Click ID. Google Ads auto-tagging adds it to the landing page URL as the gclid parameter when someone clicks an ad.

Is it safe to remove the GCLID from my URLs?

Not before your conversion tag and Google Analytics tag have read it. Removing it on the landing page, or losing it in a redirect, breaks Google Ads website conversion tracking and offline conversion imports for that click. Strip it from URLs only after the tags have stored it, such as when you clean URLs for caching or sharing.

Do I still need UTM parameters if auto-tagging is on?

Yes, if you use any analytics tool other than Google Analytics. Only Google's products can decode a GCLID, so UTM tags are what tell every other tool which campaign sent the visit. GA4 itself prioritizes auto-tagging over manual tags, so the two do not conflict there.

Why does my GCLID look different on every click?

Each GCLID identifies a specific click, so two clicks usually produce two values. Google notes one exception: a GCLID is sometimes created at impression time, and in that case a user who clicks the same ad again gets the same GCLID.

What is the difference between GCLID, GBRAID and WBRAID?

GCLID identifies a Google Ads click that lands on a website. GBRAID is used when a web ad click leads into an iOS app, and WBRAID when an ad click inside an iOS app leads to a webpage. Google recommends sending both a GCLID and a GBRAID when a conversion has both.

How long can I wait to upload an offline conversion with a GCLID?

Up to 90 days. Google's offline conversion FAQ says you can upload any conversion with a GCLID "so long as it's no longer than 90 days," because Google retains the GCLID for only 90 days, and an older click returns the error "This click is too old for its conversion to be imported." Scheduled Data Manager imports from Google Cloud Storage, Amazon S3, HTTP, SFTP and Google Sheets look back 90 days in every run, and Google's suggested capture script stores the GCLID for the same 90 days.

How do I turn auto-tagging on or off in Google Ads?

Go to Admin, then Account settings, then Auto-tagging, and check or uncheck "Tag the URL that people click through from my ad." Auto-tagging is on by default for new accounts and switches on again when you create a new conversion action, unless you use cross-account conversion tracking.

What happens if a website blocks the GCLID parameter?

A small percentage of websites do not allow arbitrary URL parameters and serve an error page once auto-tagging adds the gclid parameter to the URL. For those visits, conversion tracking has no click data to read.

Does Safari always strip the GCLID?

No. Apple takes tracking parameters out of links shared in Messages and Mail and out of links opened in Private Browsing. WebKit says the same protections run in regular tabs only when the user turns on Advanced Tracking and Fingerprinting Protection for all browsing. Apple does not publish which parameters count as click-level, so test your own ad URL in a Private Browsing window.

Why is auto-tagging required for conversion tracking?

Google calls auto-tagging "a required feature" for conversion tracking because the GCLID it adds is what links a click to what happens after it, whether that is a website conversion, a Google Analytics session or an offline sale. Google also says "Some browsers require auto-tagging to track conversions," so turning it off loses conversions from those browsers.