Every V4 UUID

Original Article ↗ Hacker News Discussion ↗

Overall reaction & concept

  • Many commenters love the project as funny, artistic, and surprisingly polished, likening it to a “Library of Babel” for UUIDs.
  • Others initially misunderstand it as a database of existing UUIDs or UUID-shaped domains before realizing it’s a deterministic generator over the full v4 space.

Implementation & technical details

  • The site enumerates all possible UUIDv4s by mapping each integer index in [0, 2^122) bijectively to a valid UUIDv4 using a Feistel-like cipher, not random generation.
  • This preserves uniqueness: each index yields exactly one UUID, and no UUID appears twice.
  • Only 122 bits are free; version and variant bits are fixed per the v4 format.

Search behavior

  • The “search” is effectively a custom full-text finder that uses the known mapping to generate UUIDs matching a substring rather than scanning stored data.
  • It does not strictly enumerate matches in order; “next/prev” can revisit different UUIDs, and mobile browser find-in-page doesn’t integrate.
  • Commenters propose more rigorous schemes (linear algebra over GF(2), T-functions, format-preserving encryption, SMT solvers) to get ordered results while retaining a random-looking sequence.

UUID format and scale

  • Several comments explain that v4 UUIDs are 128-bit values with 6 fixed bits, leaving 2^122 possibilities.
  • There is discussion of valid hex digits, version nibble 4, and allowed variant bits (8–b), and of why naïve strings like deadbeef-f00d-f00d-deadbeef are invalid.
  • People compare the keyspace size to card-shuffle factorials and cosmic-scale analogies.

Performance, UI, and browser quirks

  • Users praise how smooth and responsive the “infinite” scrolling feels compared to typical web apps.
  • Implementation uses a virtualized table and custom scroll handling because browsers cap scrollable height well below “trillion-pixel” ranges.
  • Some report edge-case bugs (e.g., scrolling past the bottom throwing errors, trackpad vs. wheel differences, mobile scroll/search limitations).

Security, privacy, and “data leaks” jokes

  • Running joke: “all UUIDs have been leaked,” paralleling lists of all ATM PINs or SSNs; people mock-check “their” UUIDs, passwords, and keys.
  • One commenter briefly worries this could be a useful rainbow table but others clarify that UUIDs are generated on the fly and cover the entire space, not a curated subset.

Ideas, feature requests, and variants

  • Requests include: bookmarking via deep links, an API, smooth/autoscroll, draggable scrollbars on mobile, Excel export, and “I’m Feeling Lucky” / scrubbing controls.
  • Many enjoy hunting for vanity/hexspeak UUIDs (e.g., deadbeef, b00b, 69420, pi) and joke about “claiming” or minting them as NFTs.
  • Some imagine similar projects for every SSN, every password, or “every UTF-8 string,” extending the Library-of-Babel theme.