Click IDs vs UTMs: What gclid and fbclid Actually Do
gclid, fbclid, ttclid, msclkid. What click IDs do, how they differ from UTM parameters, and whether you should run both. Short answer: yes, carefully.
Two tagging systems, one URL
Look at a URL from any paid ad and you'll find a mess of parameters. Some you wrote (utm_source, utm_campaign). Some the ad platform injected without asking (gclid, fbclid). They look similar, sit in the same query string, and do totally different jobs.
Marketers mix them up constantly. Then attribution breaks and nobody knows which parameter to blame. So here's the actual difference.
What a click ID is
A click ID is an opaque token the ad platform generates for every single click. It looks like garbage because it is, to you: gclid=Cj0KCQjw... means nothing to a human. To Google, it's a key that unlocks everything about the click. Which campaign, which ad group, which keyword, which device, what you bid, what it cost.
Each platform has its own:
| Parameter | Platform | Added by |
|---|---|---|
| gclid | Google Ads | Auto-tagging |
| wbraid / gbraid | Google Ads (iOS, post-ATT) | Auto-tagging |
| fbclid | Facebook / Instagram | Always appended |
| msclkid | Microsoft Ads | Auto-tagging setting |
| ttclid | TikTok Ads | Always appended |
| li_fat_id | LinkedIn Ads | Always appended |
The detail that matters: a click ID only means something inside its own ecosystem. Google Analytics can decode a gclid because Google runs both sides. Your CRM can't. A data warehouse can't. Facebook can't read a gclid, and Google can't read an fbclid. Outside its home platform, a click ID is dead weight.
What UTMs are
UTM parameters are the opposite. Plain text, readable by anything that can parse a URL. utm_source=google, utm_medium=cpc, utm_campaign=spring-sale. No platform has to decode anything. Your analytics tool, your CRM, your spreadsheet, a form's hidden fields, all of them can read UTMs directly.
The tradeoff is you have to write them yourself, and humans are inconsistent. We wrote a whole guide on naming conventions because "Google" vs "google" vs "google-ads" ruins more reports than any technical failure.
So which should you use?
Both. This isn't a versus, despite the title. They cover each other's blind spots.
Click IDs give you precision inside the platform. When GA4 sees a gclid, it pulls campaign, ad group and keyword data straight from Google Ads. More granular than anything you'd write by hand. You get that for free by leaving auto-tagging on, and you should.
UTMs give you portability everywhere else. When that lead hits your CRM three weeks later, the gclid attached to it is a meaningless string. But utm_campaign=spring-sale still reads exactly like what it is. Every tool downstream of the click needs UTMs to make sense of it.
Run auto-tagging and manual UTMs together. That's the setup Google itself recommends, and it's the one we see working across every serious ad account.
The one trap to avoid
There's a GA4 setting that decides what happens when a click has both a gclid and manual UTMs. It's called "override auto-tagged data with manually tagged data" and it lives in the Google Ads linking settings. Leave it off.
With the override on, your hand-written UTMs replace the auto-tagged data, and you lose the keyword-level detail Google would've given you. People turn it on because their UTM values "aren't showing up" for Google Ads traffic, which feels like a bug. It isn't. GA4 is preferring the richer data source. Let it.
Where your manual UTMs matter for paid traffic is everywhere GA4 isn't: the CRM, the form capture, the revenue report you build eight weeks later.
Two housekeeping notes
fbclid changes on every click. It's also appended to organic shares, not just ads. If your URLs collect fbclid and your analytics treats each URL variant as a separate page, you'll see fragmented page reports. Configure your tools to ignore it for page grouping.
Redirects can drop both. A redirect hop that strips query strings kills gclid and UTMs alike, and paid clicks land as direct traffic you paid for. If you run ads through short links, use a redirect service that passes parameters through untouched. Test it: click your own ad, check the final URL.
The mental model
Click IDs are the platform talking to itself. UTMs are you talking to every tool you'll ever use. One is rented precision, the other is owned portability.
Write your UTMs like they'll outlive the ad platform, because they will. The free UTM builder keeps the values consistent, and consistency is the entire game. Our complete UTM guide goes deeper on the parameter definitions themselves.