UUID v4 generator
What this UUID v4 generator does
Version 4 UUIDs are 128-bit identifiers with six fixed bits marking the version/variant and the remaining 122 bits filled from a random source—formatted as 8-4-4-4-12 lowercase hex. They are practically unique for distributed databases without a central allocator, though theory still says "check for collisions if your vault is cosmic-scale." This page generates v4 only; it does not emit time-sortable v1 or vendor-specific v6–v8 IDs.
When to use it
Use them for primary keys in client-created rows, correlation IDs in logs, or ephemeral upload tokens before you wire a real Snowflake service. Store canonical lowercase strings in databases; normalize hyphens per your ORM. Pair with Slug generator when URLs need human words alongside opaque IDs.
Worked example
Mobile offline queue assigns 550e8400-e29b-41d4-a716-446655440000-style IDs locally so merges reconcile once sync hits Postgres without sequence contention.
Frequently asked questions
Are UUIDs secret?
No. Anyone who guesses or intercepts one may access resources if authorization is sloppy—always enforce authz server-side.
Uppercase versus lowercase?
RFC guidance prefers lowercase generation; comparisons should be case-insensitive anyway.
Why not ordered IDs?
Random UUIDs fragment B-tree indexes slightly; time-ordered alternatives trade collisions for locality—pick per workload.