Set by Meta Pixel (used by both Facebook and Instagram Ads) to identify browsers for ad delivery, conversion tracking, and remarketing.

Stores the last-click ID (fbclid) from a Facebook or Instagram ad that brought the visitor to the site. Used for ad attribution and conversion tracking.

Set by facebook.com when Meta widgets are embedded (Like button, comments, login). Used to deliver ads, measure ad performance, and personalise ad content across Facebook and Instagram.

Browser identifier set by facebook.com. On third-party sites that embed Meta widgets (Like button, comments, Login) it enables Meta to recognise the browser across sessions — a cross-site tracking signal that requires consent.

Browser identifier used by Meta for account-recovery flows and authentication security. Surfaced on third-party sites through Meta embeds, contributing to cross-site visitor identification.

Stores the Facebook / Instagram user ID of the signed-in visitor. When a third-party page loads a Meta embed, the cookie is sent to Meta — directly identifying the visitor across the web.

Session token authenticating signed-in Facebook / Instagram users. Sent to Meta from any third-party page embedding a Meta widget while the visitor is logged in to Meta.

Stores the visitor's browser window dimensions so Meta can render embeds at the correct size. Set on facebook.com.

Stores the visitor's chat and presence state for Facebook Messenger / Instagram Direct. Session-only.

Stores the user's language preference for Meta-rendered content (Like button, embeds, Messenger).