Generate cryptographically secure UUID v4 and ULID identifiers instantly. Bulk generate up to 100 at once, copy all, and choose your preferred format. Uses crypto.getRandomValues().
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UUID v4 is generated using the browser's native crypto.randomUUID(), which produces 122 bits of cryptographically secure randomness. The format is xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx where the 4 denotes version 4 and y is a variant nibble.
For all practical purposes, yes. UUID v4 contains 122 random bits. The probability of generating two identical UUIDs across one billion UUIDs per second for 100 years is roughly 1 in a billion. In practice, collisions are not a concern for any real-world application.
Use ULID when you need IDs that sort chronologically — for example, as database primary keys in systems that benefit from sequential inserts (B-tree indexes stay hot). ULIDs are also URL-safe strings, making them easier to use in path segments without encoding. Use UUID when you need broad ecosystem compatibility (many frameworks auto-generate UUID v4).
They represent the same 128-bit value — the dashes (hyphens) in the standard form are purely cosmetic separators defined by RFC 4122. Most databases and ORMs accept both. "No dashes" format (32 hex chars) is slightly more compact and common in storage-constrained environments.
Yes. UUID v4 and ULID are both suitable as primary keys. UUID v4 inserts are random-ordered, which can cause index fragmentation on large tables in B-tree indexes. ULID avoids this because its timestamp prefix keeps inserts roughly sequential. If you use PostgreSQL, consider the native uuid type for UUIDs. For MongoDB, the default ObjectID is ULID-like (timestamp + random).