Security
UUID Generator (v4 & v7)
Generate random UUID v4 and time-ordered UUID v7 identifiers locally using native browser crypto primitives with bulk and case options.
Generated V4 Identifiers
0 UUIDsℹ️ Understanding UUID v4 vs. UUID v7 (RFC 9562)
Generated purely from 122 bits of cryptographic pseudo-randomness. Completely non-sequential, with virtually zero collision probability (1 in 2¹²²).
Best for: Temporary tokens, session identifiers, and security nonces where chronological order must be kept hidden.
Combines a 48-bit Unix timestamp in milliseconds with 74 bits of entropy. Naturally sortable chronologically, avoiding database B-tree index fragmentation.
Best for: Database primary keys (PostgreSQL, MySQL), event streams, and distributed message tracking.
Choosing Between v4 and v7 in Practice
If identifiers land in a database index, the sortability of UUID v7 is a real performance feature: rows written in sequence cluster together in the B-tree instead of scattering inserts across pages the way random v4 keys do. Teams migrating from v4 to v7 primary keys commonly report measurable write-throughput gains on large tables.
If identifiers are exposed publicly and must not reveal timing, v4 remains the right choice — every v7 UUID carries a 48-bit timestamp of its creation, which is information disclosure even though it is not a security vulnerability by itself.
Version 4 or Version 7
UUID v4 is almost entirely random, which makes collisions practically impossible but gives no ordering. UUID v7 puts a millisecond timestamp in the first bits, so new identifiers sort roughly by creation time and keep database indexes more compact.
For primary keys in large tables, v7 usually causes less index fragmentation than v4. Neither version is a secret: do not use UUIDs as passwords or access tokens unless generated from a cryptographic source, which the browser provides here.
How It Generates Output
- Generates RFC 4122 random UUID v4 using native Web Crypto crypto.randomUUID().
- Generates RFC 9562 UUID v7 embedding 48-bit millisecond unix timestamps for optimal database index clustering.
- Supports bulk batch generation (up to 50 UUIDs) with uppercase/lowercase formatting.
Example Output
Common Questions
When should I use UUID v7 over v4?
UUID v7 is ideal for database primary keys because its chronological ordering prevents B-Tree index fragmentation while retaining global uniqueness.
Are generated UUIDs safe to share publicly?
UUIDs contain no personal data. UUID v4 values are fully random and opaque, while UUID v7 embeds a 48-bit millisecond timestamp of creation, so sharing v7 values reveals rough timing information about when the ID was generated.
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