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DEVELOPER REPORTS ACTUAL UUID V4 COLLISION

INDUSTRY DESK1 MIN READ
SAT, MAY 9, 2026

■ AI-SUMMARIZED FROM 1 SOURCE ▸ TIMELINE

A developer reported an extremely rare event: a genuine UUID v4 collision in production. Two separate documents generated identical UUIDs roughly one year apart using the standard npm uuid package.

The duplicate UUID in question—b6133fd6-70fe-4fe3-bed6-8ca8fc9386cd—appeared when a new database record was inserted with a freshly generated v4 identifier that matched an existing record from 2025. UUID v4 relies on random number generation to create 128-bit identifiers. The theoretical probability of collision is astronomically low, with odds estimated at roughly 1 in 5.3 trillion for generating two identical UUIDs. The developer confirmed the duplicate wasn't caused by a double-insert bug or other system error, ruling out common causes of apparent collisions. They were using the widely-adopted npm uuid package, a standard library for UUID generation in JavaScript environments. The incident raises questions about randomness quality in UUID generation libraries and whether production systems should implement additional safeguards despite the theoretical improbability of collisions.

■ SOURCES

Hacker News

■ SUMMARY WRITTEN BY AI FROM THE LINKS ABOVE

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