Lightbeam (called Collusion in its experimental version) was an add-on for Firefox that displays third party tracking cookies placed on the user's computer while visiting various websites.

[4][5] At any time during a browsing session the user can open a separate tab, using the "Show Lightbeam" option of Tools, to display a graph of sites visited and cookies placed.

[4] Gary Kovacs, CEO of Mozilla, presented Collusion in a TED talk (Technology, Entertainment, Design) in early 2012.

[5] Stephen C. Webster, writing for The Raw Story wrote of the information provided by Collusion: "While it doesn’t sound all that creepy, just wait until you see your own graph.

[5][3][7] However, beginning in October 2019, they ended official support in favour of built in Enhanced Tracking Protection in Firefox.