fbp and fbc Parameters

This guide gives you context around _fbc and _fbp. These 2 parameters represent browser cookie values and can be sent with your server events. See About Cookie Settings For Your Facebook Pixel.

We recommend that you always send _fbc and _fbp browser cookie values in the fbc and fbp event parameters, respectively, when available. These values are subject to change over multiple browser sessions, so we recommend refreshing a user’s profile with the latest value whenever possible.

fbp

When the Facebook pixel is installed on a website, and the pixel uses first-party cookies, the pixel automatically saves a unique identifier to an _fbp cookie for the website domain if one does not already exist.

The fbp event parameter value must be of the form version.subdomainIndex.creationTime.randomnumber, where:

  • version is always this prefix: fb
  • subdomainIndex is which domain the cookie is defined on ('com' = 0, 'facebook.com' = 1, 'www.facebook.com' = 2). If you’re generating this field on a server, and not saving an _fbp cookie, use the value 1.
  • creationTime is the UNIX time since epoch in milliseconds when the _fbp cookie was saved. If you don't save the _fbp cookie, use the timestamp when you first observed or received this fbp value.
  • Randomnumber is generated by the Facebook pixel SDK to ensure every _fbp cookie is unique.

Here’s an example of what the fbp value could look like:

fb.1.1596403881668.1116446470

fbc

When a user clicks on an ad on Facebook, the link sometimes includes a fbclid query parameter. When the user lands on the target website, if the website has a Facebook pixel that uses first-party cookies, the pixel automatically saves the fbclid query parameter to an _fbc cookie for that website domain. See About Cookie Settings For Your Facebook Pixel for information on first-party cookie settings.

If the _fbc browser cookie is not available, either because there is no Facebook pixel running on the website or because first-party cookies are turned off, it is still possible to send the fbc event parameter if an fbclid query parameter is in the URL of the current page request.

The fbc event parameter value must be of the form version.subdomainIndex.creationTime.fbclid, where:

  • version is always this prefix: fb
  • subdomainIndex is which domain the cookie is defined on ('com' = 0, 'facebook.com' = 1, 'www.facebook.com' = 2). If you’re generating this field on a server, and not saving an _fbc cookie, use the value 1.
  • creationTime is the UNIX time since epoch in milliseconds when the _fbc cookie was saved. If you don't save the _fbc cookie, use the timestamp when you first observed or received this fbclid value.
  • fbclid is the value for the fbclid query parameter in the page URL.

Here’s an example of what the fbc value could look like (note that the fbclid portion is invalid):

fb.1.1554763741205.AbCdEfGhIjKlMnOpQrStUvWxYz1234567890

Learn More

  • Visit the Pixel Support guide for any issues involving missing query parameters or broken redirects.