Generate RFC 9562 UUID v4 or time-ordered v7 in bulk with case and format options.
Generate RFC 9562 UUID v4 or time-ordered v7 in bulk with case and format options. Use it for everyday work, development, learning, or quick verification.
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A UUID (Universally Unique Identifier) is a 128-bit identifier formatted as 32 hexadecimal digits in five hyphen-separated groups (8-4-4-4-12). UUID v4 uses 122 random bits alongside 6 fixed version and variant bits, making it suitable for general-purpose identifiers that do not require chronological ordering.
Standardized in RFC 9562, UUID v7 places a 48-bit big-endian Unix millisecond timestamp at the most significant bits, followed by a 12-bit monotonic counter and 62 random bits. Because the timestamp comes first, lexicographical string sorting matches creation time order, reducing B-tree index fragmentation in relational databases.
Use UUID v7 for database primary keys (such as in PostgreSQL or MySQL) and event logs where sequential insertion improves B-tree locality. Choose UUID v4 for tokens or public resource IDs when you do not want the creation time embedded in the identifier.
UUID v4 has 122 random bits (roughly 5.3×10³⁶ possibilities), while v7 combines a millisecond timestamp, a monotonic counter, and random bits. With a proper random source, collision probability is astronomically low and treated as unique in practice, though not a mathematical impossibility.
Yes, they share the same 128-bit structure and representation. GUID (Globally Unique Identifier) is the term popularized by Microsoft across Windows, .NET, and SQL Server, where uppercase digits or surrounding curly braces ({…}) are frequently used.
Yes. The first 12 hexadecimal characters of a UUID v7 directly encode the 48-bit Unix timestamp in milliseconds, which anyone can decode. If you do not want to expose creation timestamps in URLs or API responses, use UUID v4 instead.
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