UUID Generator

UUID v4 generation method and collision assumptions

The generator creates version 4 UUIDs from browser cryptographic randomness and sets the required version and variant bits. A UUID is an identifier, not a secret, password, signature, or proof that a record exists. Lowercase and uppercase display options do not change the underlying 128-bit value.

Methodology

1. The preferred implementation uses crypto.randomUUID when available.
2. A compatible fallback fills random bytes with crypto.getRandomValues, then sets the version and variant fields.
3. Bytes are formatted in the standard 8-4-4-4-12 hexadecimal layout.
4. Bulk generation repeats the same independent process and does not derive later identifiers from earlier output.

Worked review example

A value such as 550e8400-e29b-41d4-a716-446655440000 shows the expected text shape, but example values should never be copied as supposedly unique production IDs. Generate a new value at the point of record creation. Database constraints should still enforce uniqueness because application correctness should not depend only on probability.

Test coverage and expected behavior

Checks include format, hyphen positions, hexadecimal characters, version nibble 4, RFC variant bits, uppercase display, bulk count, and duplicate detection within test batches. A finite test cannot prove that collisions are impossible; it verifies implementation shape and random-source use.

Decision checklist before using the output

Choose a UUID only when a random opaque identifier fits the data model. Store it in a native UUID type when available, or validate and normalize the textual form at system boundaries. Add a database uniqueness constraint and handle the unlikely conflict path rather than assuming an insert can never collide. Do not sort version 4 UUIDs as creation time, expose them as proof of authorization, or embed sensitive meaning in adjacent URL behavior. If ordered identifiers are required for index locality or event chronology, evaluate a suitable time-ordered scheme and its privacy tradeoffs instead of rewriting a v4 value. Test serialization through APIs, databases, logs, and case-normalizing systems. The generator is appropriate for fixtures, local records, and interoperability checks; production services should normally create identifiers in the trusted application or database layer where lifecycle and constraints are enforced.

Important limitations

• UUIDs reveal no trustworthy creation time, owner, or authorization.
• Do not use UUID v4 as an authentication token without a separate security design.
• Weak or replaced browser randomness undermines the collision assumptions.
• Case-insensitive storage is normally appropriate for the textual form.

Sources and specifications

These references define the relevant format or browser behavior. They do not endorse WordCaseFix.

• RFC 9562 UUIDs
• Web Cryptography API

Last reviewed: August 6, 2026