UUID generator: create random and time-ordered UUIDs, free and private
A UUID generator creates universally unique identifiers: 128-bit values written as 32 hexadecimal digits, such as 550e8400-e29b-41d4-a716-446655440000. To generate UUIDs free and privately, choose a UUID Version (v4 is the usual pick), set Number of UUIDs to Generate between 1 and 1,000, click Generate UUIDs, then use Copy All or Download .txt. The UUIDs are made in your browser and nothing is uploaded; you can check that in the Network tab of DevTools.
The tool makes four kinds. v4 is random, v7 is time-ordered, v1 is timestamp-based and v5 is derived from a name, so the same name always gives the same UUID. As of October 2026 the current UUID standard is RFC 9562, published by the IETF in May 2024. It replaced RFC 4122 and added versions 6, 7 and 8 and the Max UUID. The UUID Validator below the generator reads versions 1 to 8.
A UUID is an identifier, not a secret. For passwords and tokens, use the password generator; for arbitrary random text, the random string generator.
Table of Use: which version to generate
| Button | What it contains | Run twice | Use it for |
|---|---|---|---|
| UUID v4 (Random) | 122 random bits from crypto.getRandomValues | Different every time | Record IDs, request IDs, file names: the default choice |
| UUID v7 (Time-ordered) | 48-bit Unix timestamp in milliseconds, then a counter and random bits | Different; later ones sort higher | Database primary keys, sortable log IDs |
| UUID v1 (Timestamp-based) | 100-nanosecond timestamp counted from 15 October 1582, a clock sequence and a random node | Different; rises within a batch | Systems that expect v1 |
| UUID v5 (Name-based) | SHA-1 of a namespace UUID plus a name | Identical for the same namespace and name | Stable IDs derived from a domain, URL or other name |
For example, v5 with the DNS namespace and the name example.com always returns cfbff0d1-9375-5685-968c-48ce8b15ae17. The validator, in turn, explains any UUID you paste:
| You paste | Validator says |
|---|---|
| 550e8400-e29b-41d4-a716-446655440000 | Valid UUID v4 |
| 017F22E2-79B0-7CC3-98C4-DC0C0C07398F | Valid UUID v7, embedded timestamp 2022-02-22 19:22:22.000 UTC |
| {550E8400-E29B-41D4-A716-446655440000} | Valid UUID v4 (braces accepted; canonical form shown in lowercase) |
| 00000000-0000-0000-0000-000000000000 | Valid Nil UUID |
| 550e8400-e29b-91d4-a716-446655440000 | Well-formed, but the version is not defined |
| not-a-uuid | Invalid UUID format |
The timestamp inside a v7 UUID is Unix time in milliseconds. To turn other Unix times into dates, use the Unix timestamp tool or the timestamp converter.
Features
- Four versions. v4, v7, v1 and v5, each with a one-line description under the UUID Version buttons.
- Batches of 1 to 1,000. The default is 10. A number outside the range is changed to the nearest limit when you leave the field (5000 becomes 1,000, 0 becomes 1), and a decimal is rounded; an empty field shows an error and generates nothing. v5 always makes exactly one.
- Uppercase and Include hyphens. Both change the list immediately, and the copied and downloaded text follows them.
- Ordered batches. v7 and v1 UUIDs made within the same millisecond still increase, so a batch comes out in order.
- v5 namespaces. DNS, URL, OID, X.500 DN or a Custom namespace UUID, plus a Name that is used exactly as typed (UTF-8, case- and space-sensitive).
- Copy and Download .txt. Copy per row, Copy All with one UUID per line, or a file such as uuids-v4.txt named after the version.
- No hardware address. The node field of a v1 UUID is random, never your computer's MAC address.
- UUID Validator. Accepts hyphenated, 32-digit, braced and urn:uuid: forms, and reports canonical form, variant, version and embedded timestamp.
- Clear. Empties the list and the validator in one click.
Need a lot of IDs in a file? Sort them with the line sorter or count them with the line counter. For a hash of some data rather than an identifier, try the SHA-256 hash generator.
How to generate a UUID, step by step
- Under UUID Version, choose UUID v4 (Random), UUID v7 (Time-ordered), UUID v1 (Timestamp-based) or UUID v5 (Name-based).
- For v5 only, pick a Namespace and type a Name, for example example.com. For the other versions, enter the Number of UUIDs to Generate, from 1 to 1,000.
- Tick Uppercase if you want capitals, or untick Include hyphens for the 32-character form.
- Click Generate UUIDs (the button reads Generate UUID for v5).
- Click Copy beside a row, Copy All for the whole list, or Download .txt to save it.
- To check an existing UUID, paste it into UUID Validator and click Validate, or press Enter. Click Clear to reset everything.
Who can use it
- Backend developers and database designers choosing v7 keys that sort by creation time, and checking what a column already holds with the validator.
- Test engineers filling fixtures with up to 1,000 IDs at a time, then shaping them into test data with the JSON formatter or the CSV to JSON converter.
- .NET and Windows developers who call them GUIDs and need a few for config files or registries.
- Integrators who need a stable ID for a record that comes from a name, which v5 gives without a lookup table; the random number generator covers plain numeric IDs.
- Students learning how version and variant bits are laid out, using the validator on the sample UUIDs above.
FAQs
Which UUID version should I use?
Use v4 for most purposes: it is random and reveals nothing about when or where it was made. Use v7 for database primary keys, because it starts with a millisecond timestamp and new keys sort after old ones. Use v5 when the same name must always give the same UUID. Use v1 only when a system expects it. Pick the version with the UUID Version buttons.
What is a UUID v7 and why use it for database keys?
A UUID v7 holds a 48-bit Unix timestamp in milliseconds, followed by random bits. Because the timestamp comes first, v7 values sort in creation order, so inserts land near the end of an index instead of at random positions, which suits primary keys. This tool also counts up inside a millisecond, so a batch from one click is in strictly increasing order.
What is the difference between a UUID and a GUID?
None in practice. UUID is the name used by the standard, RFC 9562; GUID is the name Microsoft uses in Windows and .NET. Both are 128-bit values written as 32 hexadecimal digits in an 8-4-4-4-12 pattern. Any UUID from this tool can be used where a GUID is expected. Tick Uppercase if your system prefers capitals, and untick Include hyphens for the compact form.
Can two UUIDs ever be the same?
In theory yes, in practice no. A v4 UUID has 122 random bits, so by the birthday approximation you would need about 2.7 quintillion (2.7 x 10^18) of them for a 50 percent chance of a single duplicate. That is a billion UUIDs every second for about 86 years. The tool draws them from the browser's cryptographic random number generator.
How do I find out which version a UUID is?
Paste it into the UUID Validator box and click Validate. The tool accepts UUIDs with or without hyphens, in braces, or as a urn:uuid: string. It reports the version (1 to 8), the variant, the Nil or Max special cases, and for v1, v6 and v7 the timestamp inside the UUID. Anything that is not 32 hexadecimal digits is reported as an invalid UUID format.
Can I use a UUID as a password or secret token?
No. UUID standards say implementations should not assume UUIDs are hard to guess, and v1 and v7 values even contain their creation time. A v4 UUID from this tool is unpredictable, but it is meant to be an identifier, not a credential. For passwords, API keys and reset tokens, use a dedicated password generator that lets you choose the length and character set.
Are my UUIDs generated on your server?
No. Every UUID is generated by JavaScript in your browser, and validation happens on your device too. Nothing you generate or paste is uploaded. You can check this by opening the Network tab in your browser DevTools and clicking Generate UUIDs: the list appears without any request that carries it.