UUID Generator

Common questions

Which UUID version should I generate?

Choose v4 for a random identifier with 122 random bits, v7 when an embedded Unix millisecond timestamp is useful, and v5 when the same namespace and exact name must always give the same identifier. The page generates these three versions, plus Nil and Max. It can inspect other version fields, but it does not generate v1, v3, v6 or v8.

How do I generate UUID v5 from a string?

Select V5, choose the standard DNS, URL, OID or X.500 namespace, or enter a custom namespace UUID, then type the name and press Generate UUID v5. DNS with python.org produces 886313e1-3b8a-5372-9b90-0c9aee199e5d. The namespace bytes and exact UTF-8 name are hashed with SHA-1, as required by UUID v5, then version and variant bits are set. Case, spaces and Unicode normalization change the result. An empty name is allowed, and an incomplete Unicode surrogate is refused. The name is not saved or uploaded.

What is the difference between UUID v4 and v7?

V4 is random and contains no timestamp. V7 starts with a 48-bit Unix millisecond timestamp. This generator uses a 12-bit counter inside that millisecond and 62 random trailing bits. Canonical v7 strings sort by their embedded timestamp, which can improve index locality in some databases; actual insert speed and index size depend on the database and workload. Within this tab, the counter orders values while the clock advances normally. Counter exhaustion refuses another value until the clock advances, and a backwards clock or a different tab is outside that ordering guarantee.

How do I validate a UUID or decode a v7 timestamp?

Paste the value in the inspector. It accepts 32 hexadecimal characters or complete 8-4-4-4-12 groups, optionally enclosed in balanced braces, and accepts upper or lower case. A readable representation is reported separately from a recognized version and variant. Nil and Max have special labels. Only an RFC-variant v7 gets an embedded timestamp display; the timestamp does not prove when or by whom the value was made. V4 has no timestamp to extract.

How many characters and bytes are in a UUID?

A UUID is 128 bits, or 16 bytes. Its canonical hexadecimal text has 36 characters: 32 hexadecimal digits and four dashes. No dashes gives 32 characters; braces add two more. A 16-character or 16-bit value is not a complete UUID. The output download is a UTF-8 text list, not a binary 16-byte UUID file or a shortened-ID encoding.

Can I generate UUIDs in bulk or download the list?

Use the count buttons for 1, 5, 25, 100 or 1,000 identifiers in v4 or v7. Copy all copies one UUID per line, and Download TXT saves the same formatted list with a final newline. Each row also has its own Copy button. V5 produces one deterministic result for one namespace/name pair; asking for duplicates would not create new identifiers.

What are the odds of a UUID collision?

For independent uniformly random v4 values there are 2^122 possible random-bit combinations. The birthday approximation reaches a 50% chance of a duplicate near 2.7 × 10^18 generated values; no finite batch proves global uniqueness. V7 has a different timestamp/counter/random layout and depends on clock behavior, so the v4 estimate does not describe it. V5 deliberately repeats for the same namespace and name and uses SHA-1, whose collision resistance is not suitable for security-sensitive proof of identity.

Are UUIDs passwords, API secrets or authentication tokens?

Use a purpose-built password or secret generator for those jobs. V4 draws secure randomness, but a UUID is an identifier and does not implement an application’s token lifecycle. V7 exposes its timestamp, v5 is predictable from its inputs, and Nil and Max are fixed constants.

What are Nil, Max and the UUID variant?

Nil is 00000000-0000-0000-0000-000000000000 and Max is ffffffff-ffff-ffff-ffff-ffffffffffff. They are special all-zero and all-one values. The variant bits identify a UUID layout: this tool generates the RFC variant and names legacy NCS, Microsoft and reserved variants when inspecting a value. A readable string with an unrecognized version or legacy variant is not labelled as a recognized modern layout.

Can I use generated UUIDs in Minecraft resource packs, Bluetooth services or V2Ray?

A v4 UUID can supply an identifier where an application explicitly asks you to create a new UUID, such as a resource-pack manifest or a custom 128-bit Bluetooth service. This page only supplies the identifier: it does not create a manifest, allocate an official Bluetooth 16-bit service ID, configure V2Ray or look up a player’s Minecraft UUID. An existing player identity or offline-player UUID needs that system’s own rules.

Does this provide programming libraries, SQL functions or UUID regular expressions?

It provides values and an inspector in your browser. It does not install npm or Python packages, supply Java or C# libraries, implement a SQL UUID function, debug a framework error or generate regex code. A UUID’s textual shape is also different from validating its version and variant; the inspector reports both.

Is anything generated on a server or remembered?

All identifiers and inspections are computed in this browser. Version, count, formatting and a valid namespace can be remembered on this device; names, generated UUIDs and inspection input are not saved. A subpage’s preset changes only the current view until you explicitly select each overridden setting. Start over clears the remembered settings.