What is a GUID?
A GUID (globally unique identifier) is Microsoft’s common name for an identifier that uses the UUID format. In everyday development, GUID and UUID usually refer to the same 128-bit value written as 32 hexadecimal digits in a 8-4-4-4-12 pattern.
UUIDv4: random identifiers
UUID version 4 fills the identifier’s non-version and non-variant fields with cryptographically secure random bits. It is widely supported and useful when identifiers should not reveal creation time. This tool sets the RFC version and variant bits and obtains the remaining bytes from the browser’s secure random-number generator.
UUIDv7: time-ordered identifiers
UUID version 7 stores a Unix timestamp in milliseconds in its first 48 bits and fills the remaining non-version and non-variant fields with random data. That leading timestamp makes values broadly sortable by creation time and can improve write locality in databases. Values created within the same millisecond are not promised to be strictly monotonic by this tool.
Which output format should I use?
The lowercase hyphenated form is the most portable. Uppercase and braces are common in Microsoft tooling, compact output removes hyphens for fields that require exactly 32 hexadecimal characters, and URN output adds the standards-based urn:uuid: prefix. Formatting changes the text representation, not the underlying 128-bit identifier.
Can a GUID be used as a password or security token?
No. Uniqueness is not the same as authentication or secrecy. UUIDv7 exposes its creation time, and even UUIDv4 should remain an identifier rather than a credential. Use the random token generator for security tokens and the random key generator for cryptographic key material.
Standards and generation method
UUID structure and versions follow RFC 9562, which replaced RFC 4122. Random bytes come from the browser’s Web Cryptography API. Generation happens entirely on this page.