billion laughs

noun

A type of denial-of-service attack which is aimed at parsers of XML documents, based on defining entities that expand to large numbers of copies of other entities.

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Meanings

nounbillion laughs pl (plural only)
  1. pluralplural onlycomputer securityA type of denial-of-service attack which is aimed at parsers of XML documents, based on defining entities that expand to large numbers of copies of other entities.

    The XML billion laughs DoS attack simply starts by declaring an XML document with an entity named lol (hence the name laugh gets associated with it, but in a general case it can be any valid name).

    2016, Prakhar Prasad, Mastering Modern Web Penetration Testing, Packt Publishing Ltd, →ISBN, page 193

Origin

In the most frequently cited example of such an attack, the first entity is the string lol (“laugh out loud”).

Full word history & related roots →
Cite this entry
APA

billion laughs. (n.d.). In WatkinsX Dictionary. Retrieved November 3, 2026, from https://dictionary.watkinsx.com/word/billion%20laughs

MLA

“billion laughs.” WatkinsX Dictionary, https://dictionary.watkinsx.com/word/billion%20laughs. Accessed November 3, 2026.

Chicago

WatkinsX Dictionary, s.v. “billion laughs,” accessed November 3, 2026, https://dictionary.watkinsx.com/word/billion%20laughs.

Source: billion laughs on Wiktionary, CC BY-SA 4.0.