How to Capture fbclid for Meta Offline Conversions
Meta needs more than an email to match your offline sales. Here is how to capture fbclid and the _fbp cookie, and what to do with them.
This post covers how to capture the two identifiers Meta needs to match your offline sales back to ad clicks: the fbclid parameter and the _fbp cookie. Capture both and your match rates go from disappointing to genuinely useful.
Most businesses sending offline conversions to Meta send only a hashed email and wonder why half of it does not match.
When this fits
You generate leads from Meta Ads and close them somewhere else. A call, a showroom, a sales rep.
You want Meta to optimise toward real customers instead of cheap form fills.
You already send offline events and the match rate is underwhelming.
If your entire funnel completes on your website in one session, you do not need this. A properly configured pixel and Conversions API pairing covers you.
What you will capture
Three things, in order of how much they help:
fbclid. Appended to your landing page URL on a click from Facebook or Instagram. The strongest single signal.
_fbp. A first party cookie the pixel sets on your own domain, identifying the browser.
Hashed email and phone. Collected at form submission. Always send these too.
There is also a _fbc cookie, which the pixel derives from fbclid. If the pixel is installed, you can read _fbc directly instead of assembling it yourself, which is less error prone.
How it works
Someone clicks your ad, lands with an fbclid, fills in a form. You store fbclid, _fbp and their contact details on the lead record. Three weeks later they sign a contract. You send an offline event to Meta containing the outcome plus those stored identifiers, and Meta connects it back to the original click.
Let’s implement it
Step 1: capture fbclid on landing
Same rules as every other click ID. Read it from the URL on first landing, write it to a first party cookie, never overwrite an existing value with a blank one, and give it a long expiry.
Step 2: read the _fbp and _fbc cookies
These are set by the Meta pixel on your own domain, so your own JavaScript can read them. Grab both at form submission time rather than on landing, because _fbp may not exist yet on the very first page view.
Step 3: get them into hidden fields
Add hidden fields for fbclid, fbp and fbc to every form, populated from those cookies. If your form is embedded in an iframe, pass the values as URL parameters to the embed instead.
Step 4: store and hash
Write them to dedicated CRM fields. Store email and phone as normal, and hash them at upload time rather than storing hashes, so you keep the raw values for your own use.
Hashing rules that people get wrong: lowercase and trim before hashing, use SHA256, and put phone numbers in E.164 format first. A stray space changes the hash and the match fails silently.
Step 5: send the event
Send it through the Conversions API with an action source indicating it happened offline, the real event time, and a value if there is revenue attached. The full version of that is here: sending CRM outcomes to Meta as offline events.
Before you finish
Click one of your own live Meta ads, submit a test form, and confirm fbclid and _fbp both landed on the record.
Check your event match quality in Meta Events Manager after a test batch.
Confirm your hashing is normalised. Compare a known email’s hash against a hash you generate separately.
Confirm the event time you send is the real outcome time, not the upload time.
FAQ
Is fbclid enough on its own?
It is the strongest signal but not sufficient alone. Send hashed email and phone alongside it. More identifiers means a better match rate, and Meta uses whatever you give it.
How long can I wait before sending the event?
There is an attribution window beyond which Meta will accept the event but not attribute it, currently around 62 days. If your sales cycle is longer, optimise toward an earlier stage and keep closed deals for your own reporting.
What if the visitor used an ad blocker?
The fbclid is in the URL, so you still get it. The _fbp cookie may be missing because the pixel never loaded. This is exactly why capturing the URL parameter matters more than relying on the pixel.
Does this work for Instagram?
Yes. Instagram traffic carries fbclid the same way, because it is all Meta infrastructure.
Need this built properly?
Meta can only optimise toward outcomes you actually show it. I set up and repair tracking for ecommerce stores and lead generation businesses, so the numbers in your ad accounts match the money in your bank account.
Have a look at what I do, or book a call and we can go through your setup together.
