UUID / GUID Generator

Step-by-step guide

1. 1
   Select a UUID version
   Choose v4 for a random UUID (most common), v1 for a time-based UUID, v3 for a name-based UUID using MD5, or v5 for name-based using SHA-1.
2. 2
   Configure namespace and name (v3/v5 only)
   For v3 and v5, select a namespace (DNS, URL, OID, X500, or custom) and enter a name string. The same name and namespace always produce the same UUID.
3. 3
   Choose a format
   Select Standard (lowercase with dashes), Uppercase, or No Dashes depending on your system's requirements.
4. 4
   Set the count
   Enter how many UUIDs to generate at once (up to 50). v3 and v5 with the same inputs will produce identical UUIDs for each position.
5. 5
   Generate and copy
   Click Generate. Hover over any UUID to reveal a copy button, or use Copy All to copy the full list.

Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier), also called GUID, is a 128-bit identifier formatted as 8-4-4-4-12 hexadecimal characters separated by hyphens (e.g. 550e8400-e29b-41d4-a716-446655440000). They are used to uniquely identify records, files, sessions, and resources across distributed systems without central coordination.

What is the difference between UUID v1 and v4?

UUID v1 is based on the current timestamp and MAC address, making it time-sortable but potentially leaking hardware information. UUID v4 is randomly generated with no sequential structure. v4 is more commonly used and preferred when privacy matters.

What are UUID v3 and v5 used for?

v3 and v5 are deterministic: the same namespace and name always produce the same UUID. This is useful for generating stable identifiers from names: for example, always generating the same UUID for the URL 'https://example.com'. v5 (SHA-1) is preferred over v3 (MD5) for new applications.

Is UUID v4 truly unique?

With 122 random bits, the probability of generating a duplicate UUID v4 is astronomically small. To have a 1-in-a-billion chance of collision you would need to generate approximately 103 trillion UUIDs. For practical purposes, v4 UUIDs can be considered globally unique.

What is the 'No Dashes' format used for?

Some databases, programming languages, and APIs prefer UUIDs without hyphens as a 32-character hex string. The No Dashes format produces this variant. Both formats represent the same 128-bit value.

Can I use UUID as a database primary key?

Yes, UUID v4 is widely used as a primary key in distributed systems where you cannot rely on auto-incrementing integers. However, random UUIDs can cause index fragmentation in databases optimised for sequential inserts. UUID v7 (not yet in this tool) addresses this with time-ordered randomness.

Does this tool use crypto.randomUUID()?

UUID v4 generation uses the uuid library which uses crypto.getRandomValues() internally for cryptographically secure randomness. UUID v1 uses a timestamp-based approach. v3 and v5 use MD5 and SHA-1 respectively.

What is the DNS namespace for v3/v5 UUIDs?

The DNS namespace is a predefined UUID (6ba7b810-9dad-11d1-80b4-00c04fd430c8) used as a seed when generating name-based UUIDs from DNS hostnames. This ensures that UUID('example.com', DNS) is the same for everyone generating it.