Generate UUID v1, v4, and v5 instantly. Bulk generate up to 1000 UUIDs in one click. Runs entirely in your browser.
v4 (Random) — 122 bits of randomness. Best choice for database IDs, tokens, and file names. No information about when or where it was created.
v1 (Timestamp) — Embeds the current time and a random node ID. Sortable by creation time, but the time information is embedded.
v5 (Namespace + Name) — SHA-1 based. Always generates the same UUID for the same namespace+name combination. Useful for consistent IDs from known data.
Click any UUID in the list to copy it individually.
UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. It is represented as 32 hexadecimal digits in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are used as unique IDs for database records, API keys, session tokens, and file names.
UUID v1 is generated from the current timestamp and MAC address — it embeds time information but may expose your machine's MAC. UUID v4 is completely random (122 random bits) — the most widely used version for general unique IDs. UUID v5 is deterministic — given the same namespace and name, it always generates the same UUID using SHA-1 hashing. Use v4 for random IDs, v5 for reproducible IDs from known inputs.
UUID v4 has 2^122 possible values (~5.3×10^36). The probability of generating two identical v4 UUIDs is astronomically small — you would need to generate 1 billion UUIDs per second for 86 years to have a 50% chance of a single collision. For practical purposes, they are unique.
Yes. UUIDs are excellent primary keys when you need globally unique IDs across multiple databases or services, or when you want to generate IDs client-side without a round trip to the database. The trade-off is that they use more storage (16 bytes) than integer IDs and can be slower to index in large databases due to random ordering.
A nil UUID is all zeros: 00000000-0000-0000-0000-000000000000. It is defined in RFC 4122 and is used as a sentinel value to indicate 'no UUID' or an unset UUID field — similar to null in programming.