edge case

Noun

edge case (plural edge cases)

1. A problem or situation that occurs only at an extreme (maximum or minimum) operating parameter or under other unusual operating conditions.
2. (broadly) Any extremely rare situation.
   • (It's possible that at least some of the liberals who answered "yes, violence can sometimes be justified" had in mind edge cases like armed resistance by Jews against the SS, not the assassination of peaceful political pundits with whom they disagree.)2025 September 16, Jack Nicastro, “J.D. Vance Says 26 Percent of Young Liberals Justify Political Violence. Here's What the Data Really Say.”, in Reason, archived from the original on 06 Oct 2025
3. (broadly) Any unexpected input or user behaviour.
   • The first thing to do is analyze the situation and determine whether the need to provide additional use is an edge case, or if it will become a common use-case scenario.2010, Charles Edge, William Barker, Beau Hunter, Gene Sullivan, Ken Barker, Enterprise Mac Security: Mac OS X Snow Leopard, Apress, →ISBN, page 96
   • One edge case is when the code processing the message has not finished, but the invisibility window lapses, and another copy of the same message gets dequeued. At this point, there are two active copies of that message being processed.2012, Bill Wilder, Cloud Architecture Patterns, "O'Reilly Media, Inc.", →ISBN, page 32

   Synonyms:

   corner case