fbc and fbp Builder & Checker for Meta Conversions API

How to use the fbc fbp builder

This tool does two jobs for the Meta Conversions API. It builds the fbc click ID from a landing page URL, and it checks fbc and fbp values you already send, following Meta's fbp and fbc parameters page.

1. Choose a mode. Pick Build an fbc value when your server has the fbclid but no _fbc cookie. Pick Check fbc / fbp values to test values from your logs.
2. Paste the landing page URL. The tool finds fbclid= and copies its value without changing a single character.
3. Set the click time. Use the moment your site first saw the click. If you stored it as a Unix timestamp in seconds, the tool converts it to milliseconds and tells you.
4. Copy the result. You get the fbc value and a ready user_data snippet for your Conversions API event.
5. Check in bulk. In check mode, paste up to thousands of values, one per line, and download the results as CSV.

What to do next

1. Add fbc and fbp to every server event. Put them inside user_data, unhashed, next to the hashed email and phone. Meta recommends sending fbc with every event when you have it.
2. Prefer the cookie when it exists. If the Meta Pixel already set _fbc and _fbp cookies, read them on your server and send them as they are. Build fbc yourself only when there is no cookie.
3. Keep the click time from the first visit. Store the fbclid and its timestamp when the visitor lands, not when they buy days later, so the creation time stays correct.
4. Test before going live. Send a test event with a test event code in Events Manager and check that the event shows the click ID and browser ID parameters.

Common fbc and fbp errors and how to fix them

Creation time in seconds instead of milliseconds

The third part must have 13 digits. A 10-digit number like 1554763741 is in seconds — the most common fbc mistake. Multiply it by 1,000. The checker flags this on every row.

A lowercased or edited fbclid

Meta says the ClickID is case sensitive and must not be changed. Some CRMs, form tools and spreadsheets lowercase text or turn characters into codes like %2D. Store the raw value from the URL in a plain text field.

Hashed fbc or fbp

If your integration hashes every field in user_data, the click and browser IDs become useless 64-character strings. Exclude fbc and fbp from hashing.

Wrong subdomain index

Meta's examples use 0, 1 or 2 for the second part. When you build the value on a server, Meta asks for 1. A cookie set on a longer domain (like a .co.uk shop) can show a higher number; send that unchanged.

fbc sent for visits without an ad click

There is no fbc without an fbclid. Do not invent one or reuse an old one for a new visitor — send fbp and customer details instead.

Values with an appendix

Values made by Meta's Parameter Builder Library end with an extra 8-character (or older 2-character) part. That is expected and valid — do not cut it off.