What UUID versions exist?

Common versions are v1 (timestamp+MAC), v3 (MD5 namespace), v4 (random), v5 (SHA-1 namespace), and v7 (timestamp+random). v4 is the most widely used.

Is UUID validation case-sensitive?

No. UUIDs are hexadecimal and case-insensitive per RFC 4122. Both uppercase and lowercase are valid.

A NIL UUID is all zeros (00000000-0000-0000-0000-000000000000) and represents the absence of a UUID value.

UUID Validator

ID Tools

Validate UUID format and detect version

By DevToolHQ teamUpdated 2026-04-15100% client-sideMethodology

100% client-side processing

Paste UUID

About UUID Validator

Validates whether a string is a properly formatted UUID and identifies its version. The tool checks the format against the RFC 4122 pattern (8-4-4-4-12 hex digits with correct version and variant bits) and reports which version (1 through 5, plus v7, or NIL) the UUID belongs to. UUID versions differ in how they are generated. V1 encodes the MAC address of the generating host and a timestamp — it is unique but leaks information about the machine. V3 and V5 are deterministic: they hash a namespace and a name (using MD5 and SHA-1 respectively), producing the same UUID for the same inputs every time — useful for content-addressable identifiers. V4 is fully random. V7 is timestamp-prefixed random. The validator is particularly useful when debugging systems that receive UUIDs from external sources and need to distinguish between versions, or when checking whether a UUID field in an API response actually conforms to the standard before parsing it. The NIL UUID (all zeros) is a valid UUID value representing "no UUID" — some systems use it as a sentinel value and it is worth detecting explicitly. Case-insensitive validation handles both uppercase and lowercase hex characters correctly.