UUID Validator

What Makes a UUID Structurally Valid?

A UUID is a 128-bit label encoded as 32 hex digits in five hyphen-separated groups — the canonical 8-4-4-4-12 layout, 36 characters total including dashes: xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx. M is the version character, N encodes the variant. Some systems wrap the text in curly braces, but braces aren't part of the canonical structure. To generate uuid v4 without code, press the button on the UUID v4 Generator page — ready in milliseconds.

What This Validator Checks

Submitting a UUID runs it through several structural checks:

• Overall length — exactly 36 characters (32 hex digits plus four dashes)
• Hyphen placement — dashes must appear at positions 9, 14, 19, and 24
• Character set — every non-dash character must be a valid hex digit (0–9, a–f, case-insensitive)
• Version digit — the first character of the middle segment must fall in the recognized range for standard and newer UUID types
• Variant bits — the first character of the fourth block must match a known variant pattern

The strict check this tool applies:

/^[0-9a-f]{8}-[0-9a-f]{4}-[1-8][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i

A looser pattern additionally accepts optional hyphens and surrounding braces before falling back to the strict check — so {550E8400E29B41D4A716446655440000} and the canonical hyphenated form both validate correctly.

Bulk Validation

Paste multiple UUIDs, one per line, into the Bulk UUID Validation section below and every entry is checked independently — useful for auditing exports, test fixtures, or database migrations containing many labels at once. The summary shows running Valid and Invalid counts alongside per-line results. The uuid v1 generator is useful for event logging and audit trails where chronological ordering matters.

Worked Examples

Valid — a UUID v4: 550e8400-e29b-41d4-a716-446655440000. Version character "4" matches the recognized range; variant character "a" falls within [89ab], confirming the RFC 4122 variant. Result: valid.

Invalid — a truncated string: 550e8400-e29b-41d4-a716. Only four groups instead of five, 24 characters instead of 36 — the check fails immediately. Common causes of malformed entries include extra characters, non-hex characters, missing hyphens, or a version digit outside the valid range.

Special case — the Nil UUID: 00000000-0000-0000-0000-000000000000 carries no version or variant information at all. It's intentionally excluded from the strict version check but explicitly accepted as a reserved value — this tool reports it as "Valid (Nil)" rather than rejecting it.

Validating UUIDs Programmatically

To replicate this check in your own code rather than pasting values into a browser tool, most ecosystems have a well-maintained library rather than a hand-rolled regex:

• JavaScript / Node.js — the uuid npm package exports a boolean validate() function
• TypeScript / NestJS — class-validator's @IsUUID() decorator validates DTO properties directly
• JSON Schema — ajv supports the format: 'uuid' keyword natively
• General-purpose validation — the validator library's isUUID(str, version) covers v3 through v5 alongside other input types

Frequently Asked Questions