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UUID v4 is the random variant defined by RFC 4122. Out of the 128 bits, six are reserved to encode version and variant, leaving 122 random bits. This tool sources those random bits from the browser crypto API and formats the result as a standard 8-4-4-4-12 hex string. Version 4 is the right choice when you want identifiers without any ordering, time, or MAC information leaking through.
When multiple writers insert into the same table, v4 UUIDs prevent collisions without coordination.
Generate one UUID per request at the edge and thread it through downstream services for end-to-end tracing.
Assign stable random-looking IDs to seed data so tests do not depend on auto-increment order.
Send a fresh UUID v4 on each request so the server can safely retry without double-applying side effects.
122 bits of entropy is enough that practical collisions are astronomically unlikely even at very high generation rates.
If you need rough time ordering, v7 is a better fit. v4 is preferred when you explicitly want no temporal information in the identifier.
Yes. All characters are hex digits and dashes, no percent-encoding is required.
Yes. After the page loads, new UUIDs are generated locally with no network calls.