Lumen, formerly Chilling Effects, is an American collaborative archive created by Wendy Seltzer and operated by the Berkman Klein Center for Internet & Society at Harvard University.

The archive was founded in 2001 by Internet activists who were concerned that the unregulated private practice of sending cease-and-desist letters seemed to be increasing and was having an unstudied, but potentially significant, "chilling effect" on free speech.

[2] The incident inspired vocal Internet users and groups to complain to Google, and links to the Clambake site were restored.

[7] The Copyright Alliance has criticized Lumen for republishing lists of URLs named in takedowns as part of its database.

It argued that this defeats the purpose and intent of sending takedown notices to search engines in the first place, as they would subsequently be added to "the largest repository of URLs hosting infringing content on the internet.".