li_fat_id
li_fat_id stands for LinkedIn First-Party Ad Tracking ID. It is a click ID that LinkedIn appends to the landing page URL every time someone clicks a LinkedIn ad, provided enhanced conversion tracking is enabled on the account’s Insight Tag. The value identifies that specific click, which lets LinkedIn match a later conversion back to the ad that produced it.
Why li_fat_id Matters
li_fat_id is LinkedIn’s answer to third-party cookie loss. Browser restrictions and ad blockers broke the old cross-site model, so LinkedIn moved the identifier into the URL and into a first-party cookie set on the advertiser’s own domain.
Three things depend on it:
- Conversions API match rates. LinkedIn’s documentation calls capturing click IDs “critical to power the Conversions API for improved match rates.” Sending a conversion without an identifier means LinkedIn often cannot attribute it.
- Lead form and CRM attribution. The value can be stored in a hidden form field, carried into a CRM, and sent back weeks later when the deal closes.
- Campaign optimization. LinkedIn’s bidding needs confirmed conversions to learn from. Missing click IDs mean weaker signals and worse delivery.
How li_fat_id Works
Four steps, in order:
- Enable it. Turn on enhanced conversion tracking (first-party cookies) for the Insight Tag in Campaign Manager. LinkedIn enables this by default on newly created Insight Tags. Developers can set
firstPartyTrackingEnabledtotruethrough the Partial Update Insight Tag API instead. - Click. A member clicks the ad. LinkedIn appends the parameter to the destination URL.
- Capture. The site reads the value from the URL, or reads the
li_fat_idcookie that the Insight Tag writes. The cookie persists for 30 days from the most recent ad click. - Send. The stored value goes back to LinkedIn with the conversion event, as the user match identifier
LINKEDIN_FIRST_PARTY_ADS_TRACKING_UUID.
A tagged URL looks like this:
https://linkutm.com/pricing?li_fat_id=8f36a4c1-9d2e-4b77-a5f0-1c3e9b70d245
The value is a UUID. It carries no readable meaning, which is normal for a click ID.
Reading it from the URL works even without the Insight Tag installed on the page:
const li_fat_id = (new URLSearchParams(window.location.search)).get("li_fat_id");
That approach limits view-through attribution. Reading the cookie instead supports view-through conversions for members who clicked an ad in the previous 30 days.
li_fat_id vs UTM Parameters
They solve different problems and belong on the same URL. A UTM is readable text a marketer writes. li_fat_id is an opaque value LinkedIn generates and only LinkedIn can interpret.
| li_fat_id | UTM parameters | |
|---|---|---|
| Created by | LinkedIn, automatically | The marketer, manually |
| Read by | LinkedIn (Insight Tag, Conversions API) | GA4 and other analytics tools |
| Readable | No, it is a UUID | Yes, plain words |
| Scope | LinkedIn Ads only | Any channel |
GA4 ignores li_fat_id entirely. Without UTM tags, LinkedIn ad traffic can land in GA4 as direct or unassigned, so tag the same destination URLs with a LinkedIn UTM builder and let each system read the parameter it understands. li_fat_id is LinkedIn’s entry in the wider click ID family, alongside Google’s GCLID and Meta’s FBCLID.
Common li_fat_id Issues
- The parameter is stripped before the page loads. Client-side JavaScript, especially in single-page apps, can rewrite the URL before anything reads it. LinkedIn recommends firing the Insight Tag early, in the header, ahead of other libraries.
- Redirects drop it. A shortener, a consent gate, or a redirect to a third-party booking tool can lose the query string. Carry
li_fat_idthrough every hop. - Tag managers discard it. Google Tag Manager and Doubleclick can drop unrecognized parameters unless
li_fat_idis explicitly allowed. - The server rejects the URL. Some web servers and firewalls reject requests carrying unknown query parameters. Allowlist the parameter.
- Safari shortens the window. Apple’s Intelligent Tracking Prevention caps script-written first-party cookies at seven days, so the 30-day cookie window is not reliable on Safari and iOS. Capturing the value into your own database at click time avoids the problem.
Frequently Asked Questions
What does li_fat_id stand for?
li_fat_id stands for LinkedIn First-Party Ad Tracking ID. The “fat” in the middle is an abbreviation of “first-party ad tracking”, not a word. LinkedIn appends it to ad landing page URLs so conversions can be matched to clicks without relying on third-party cookies.
How do I enable li_fat_id on my LinkedIn ads?
Enable enhanced conversion tracking, previously called first-party cookies, on the Insight Tag in Campaign Manager. LinkedIn turns this on by default for newly created Insight Tags, so most accounts already have it. Once active, LinkedIn appends li_fat_id to every ad click URL automatically, with no change needed to the destination URLs in your campaigns.
Where do I find the li_fat_id value?
Read it from the landing page URL query string, or from the li_fat_id first-party cookie that the Insight Tag writes. URL parsing works even when the Insight Tag is not installed on that page, but it limits view-through attribution. Most implementations capture the value into a hidden form field so it travels with the lead.
How long does the li_fat_id cookie last?
The li_fat_id cookie persists for 30 days from the most recent ad click that landed on a page carrying the Insight Tag. Safari and iOS cut that short, because Intelligent Tracking Prevention limits script-set cookies to seven days. Store the value server-side if your sales cycle runs longer than the cookie.
Is li_fat_id the same as a LinkedIn conversion?
No. li_fat_id identifies a click, not an outcome. It becomes useful only when it is sent back to LinkedIn attached to a conversion event, either by the Insight Tag or through the Conversions API. Conversion tracking is the system; li_fat_id is the identifier that system matches on.
To tag the LinkedIn ad destination URLs that GA4 actually reads, use the free UTM builder at linkutm.