How to use the UUID generator
- 1Choose Version: v4 (random) or v7 (time-ordered). One UUID is ready when the page loads.
- 2Set How many (up to 10,000) and the format: Upper case, Hyphens, {Braces}, Quotes and Separate with.
- 3Press Generate, then Copy all or Download the list as a text file.
- 4To check an existing ID, paste it into Validate or inspect a UUID to see its version, variant and, for v1, v6 and v7, when it was created.
Example
01920f2c-6e4b-7c3a-9f12-3b4c5d6e7f80 (pasted into Validate or inspect a UUID)
Valid UUID format Version: 7 (Unix time + random) Variant: RFC 9562 / RFC 4122 Created: 2024-09-20T11:23:43.051Z
The first 12 hex digits (01920f2c6e4b) are the creation time in milliseconds since 1970; the 7 after the second hyphen is the version.
UUID v4 vs v7 (and v1)
A UUID is a 128-bit identifier written as 32 hex digits in the pattern 8-4-4-4-12. The first digit of the third group is the version.
- v4 is 122 random bits. It reveals nothing about when or where it was made. This page uses
crypto.randomUUID(), your browser's cryptographically secure generator. - v7 (RFC 9562, 2024) starts with a 48-bit Unix timestamp in milliseconds, followed by random bits. New IDs sort after older ones, which keeps database indexes compact. Here, IDs generated in the same millisecond also use a 12-bit counter so they stay in order.
- v1 combines a timestamp with the machine's network card address, which leaks hardware identity. RFC 9562 recommends v7 instead, so it isn't offered.
UUID vs GUID
GUID (globally unique identifier) is Microsoft's name for the same thing. Windows, .NET and SQL Server (uniqueidentifier) generate standard UUIDs, usually version 4. The differences are presentation: Microsoft tools often show GUIDs in upper case and wrapped in braces, {6F9619FF-8B86-D011-B42D-00C04FC964FF}. Tick Upper case and {Braces} to get that format. One real difference: .NET's Guid.ToByteArray() stores the first three groups in little-endian order, so the same GUID has a different byte order in a binary column than in a string.
Bulk generation and formats
Generate up to 10,000 IDs at once, for seeding a test database or a spreadsheet. Separate with puts them on new lines, or separates them with commas or spaces; with Quotes set to double quotes and commas, the output pastes straight into a JSON array or a SQL IN (…) list. Hyphens off gives the 32-character form that some systems store, and Upper case matches Microsoft conventions. Formatting doesn't change the value: F47AC10B58CC4372A5670E02B2C3D479 and f47ac10b-58cc-4372-a567-0e02b2c3d479 are the same UUID.
Validating a UUID
Paste any value into Validate or inspect a UUID. It accepts upper or lower case, with or without hyphens, braces, quotes or a urn:uuid: prefix, and shows the canonical lower-case form. It checks the version digit (1–8) and the variant bits (the first digit of the fourth group should be 8, 9, a or b). For v1, v6 and v7 it decodes the creation time. The nil UUID (all zeros) and the max UUID (all f) are recognized as the special values RFC 9562 defines.
Collision odds
With 122 random bits there are 5.3 × 10^36 possible v4 UUIDs. By the birthday bound you would need to generate about 103 trillion (1.03 × 10^14) of them for a one-in-a-billion chance that any two match, and about 2.7 × 10^18 for even odds. In practice, collisions come from broken random generators, not from the maths, which is why this page uses the browser's cryptographic source. v7 trades some randomness for the timestamp: 62 random bits per millisecond here, still far more than any single system generates in that time.
Is anything I enter stored?
This tool runs entirely in your browser. Your text is not uploaded to our servers.