fbclid
Also called Facebook click ID, Meta click identifier
fbclid is a parameter Meta adds to the URL when someone clicks a link on Facebook or Instagram. The Meta pixel saves it in the _fbc cookie so a later purchase can be matched to the click. It shows a visit came from Meta, but not that it came from an ad, because organic clicks often carry one too.
Sailesh B · Last updated
What it looks like
When someone taps a link on Facebook or Instagram, Meta adds a parameter to the URL before sending them on:
https://yourstore.com/products/linen-shirt?fbclid=IwZXh0bgNhZW0CMTEAAR2x...The value is a long, random-looking string. It's case-sensitive, and Meta says not to change it in any way, including lowercasing it. It means nothing to you. To Meta it points back to the click, so a purchase can later be matched to it.
fbclid doesn't mean the visit was paid
Meta's documentation describes fbclid in the context of ad clicks. In practice, Meta adds it to outbound clicks from organic posts and shared links as well, and has done since fbclid first appeared in October 2018. Meta doesn't document this, but you can check it yourself: tap a link in one of your own organic posts and look at the URL your store receives.
So a visit with fbclid in the URL tells you two things for certain. It came from Facebook or Instagram, and someone clicked. It doesn't tell you whether you paid for that click.
To prove a click was paid, you need something only an ad link carries: a paid utm_medium such as paid_social or cpc, or an ad ID parameter you added in the ad's URL parameters.
Example: two visits, one ad
Two shoppers land on the same product page from Instagram on the same day:
1. /products/linen-shirt?fbclid=IwZXh0bgNh...
2. /products/linen-shirt?utm_source=instagram&utm_medium=paid_social&fbclid=IwZXh0bgNh...The first tapped a link in an organic post. The second tapped an ad. Both carry fbclid.
- A tool that treats every
fbclidvisit as Meta Ads credits both to your ad spend. Your ROAS looks better than it is, and organic social looks like it does nothing. - GA4 ignores
fbclidand uses source, medium and referrer. Visit 2 goes to Paid Social. Visit 1 goes to Organic Social, or to Direct if the in-app browser dropped the referrer. - Prism puts visit 2 in Meta paid and visit 1 in Meta organic.
How fbclid becomes the _fbc cookie
The Meta pixel reads fbclid from the landing URL and stores it in a first-party cookie called _fbc, in this format:
fb.1.1793350800000.IwZXh0bgNhZW0CMTEAAR2x...That's a fixed fb prefix, a subdomain index (1 for a cookie set on yourstore.com), the time the cookie was created in milliseconds, then the fbclid itself. The pixel sets it to last 90 days, which is also Meta's recommended lifetime if you set it yourself. A later visit with a new fbclid replaces it.
When your store sends a purchase to Meta, the _fbc value goes with it, in the browser event and as the fbc field in the Conversions API. It's one of the strongest signals Meta has for matching the sale to the click.
When fbclid gets lost
If fbclid never reaches your store, no _fbc cookie is set and Meta has to match the purchase on weaker signals like email, phone or IP address. Common causes:
- Redirects and link shorteners that drop the query string on the way through.
- Safari's Link Tracking Protection, which strips known click IDs including
fbclidin Private Browsing and in links opened from Mail and Messages. - Apps or scripts that rewrite the URL, for example by lowercasing or trimming parameters.
- The shopper coming back later by typing your URL. The new visit has no
fbclid, though the_fbccookie from the first visit may still be there.
To check yours, click one of your own ads on your phone and look at the landing URL. If fbclid and your UTMs aren't there, something in between is removing them.
Should you strip fbclid from your URLs?
No. The pixel has to read it on the landing page, and removing it early means no _fbc cookie and weaker matching in Meta. Duplicate URLs aren't a real SEO problem here, because your store's canonical tag already points search engines at the clean product URL.
How this shows up in Shopify
Shopify assigns a visit's channel from its UTM tags and referring site, not from fbclid. That makes your UTMs the deciding factor. A Meta ad without UTMs can be reported as social traffic rather than a paid campaign, or as direct if the in-app browser hid the referrer.
The fix is to tag every Meta ad with UTMs, including a paid medium. Our UTM setup guide has the exact values.
How Prism handles it
Prism never treats fbclid alone as proof of a paid click. A visit counts as Meta paid only when the link also carries paid evidence, such as a paid utm_medium or a Meta ad ID parameter. A visit with fbclid and nothing else counts as Meta organic, so organic Facebook and Instagram sales aren't credited to your ad spend.