Generate UUIDs
All generation happens in your browser using the Web Crypto API. Version 7 uses a 48-bit timestamp prefix plus 74 random bits (RFC 9562). The URN prefix is applied only to the hyphenated form.
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Output formats
Pick the format that fits your stack. All formats below are produced from the same UUID.
- Standard (hyphenated):
123e4567-e89b-42d3-a456-426614174000 - Uppercase:
123E4567-E89B-42D3-A456-426614174000 - No hyphens:
123e4567e89b42d3a456426614174000 - Braces:
{123e4567-e89b-42d3-a456-426614174000} - URN:
urn:uuid:123e4567-e89b-42d3-a456-426614174000
Generate a UUID in your language
Frequently asked questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify information in computer systems. It is usually written as 32 hexadecimal characters split by hyphens into 8-4-4-4-12 groups, e.g.
123e4567-e89b-12d3-a456-426614174000.How is a UUID generated?
This tool generates version-4 and version-7 UUIDs. It uses your browser's cryptographically secure random number generator to fill the random portion of the 128 bits, then sets the version bits (the 13th hex digit) and the variant bits (the 17th hex digit to 8, 9, a, or b) as required by RFC 4122 and RFC 9562. No data is sent to any server.
Can a UUID generate a duplicate?
In practice, no. A v4 UUID has 122 random bits, and a v7 UUID has 74 random bits, giving an astronomically large number of possible values. The probability of a collision is so low that it is considered negligible for any realistic workload. Uniqueness is probabilistic, not guaranteed by a central authority.
What is the difference between UUID v1 and v4?
UUID v1 is time-based and embeds a timestamp plus a MAC address, which can leak machine identity. UUID v4 is purely random and is the recommended choice for most applications, including database primary keys and API tokens. v7 adds a leading timestamp for index-friendly ordering.
Should I use UUID v4 or v7?
Use v4 (random) for general-purpose IDs: it is the default in most languages and leaks nothing. Use v7 (time-ordered, RFC 9562) when the UUID becomes a database primary key, because its leading 48-bit timestamp keeps inserts roughly sequential, which reduces B-tree page splits and improves index locality. v7 still contains 74 random bits, so collision risk stays negligible.
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