Scrawlspace › Developer Utilities
UUID Generator (v4, v7), ULID & NanoID
Generate random UUID v4, time-ordered UUID v7, ULID and NanoID identifiers, up to 500 at a time, or paste an ID to see its version, variant and when it was made. IDs are made in your browser with a cryptographically secure random source, following RFC 9562.
How to use UUID / ID Generator
- Choose the ID type: UUID v4, UUID v7, ULID or NanoID.
- Set How many. For UUIDs, toggle Hyphens, Uppercase and {Braces}; for NanoID, set the Length and Alphabet.
- Click Copy on one ID, or Copy all.
- Paste any UUID or ULID into Inspect an ID to read its type, version, variant and creation time.
Frequently asked questions
What is the difference between UUID v4 and v7?
UUID v4 is fully random. UUID v7 starts with a millisecond Unix timestamp, so IDs created later sort after earlier ones. That keeps database index inserts in order, which makes v7 a better primary key.
Is a GUID the same as a UUID?
Yes. GUID is Microsoft's name for a UUID. Turn on {Braces} and Uppercase for the Windows and .NET style, for example {3F2504E0-4F89-41D3-9A0C-0305E82C3301}.
What is a ULID?
A ULID is a 26-character, time-sortable ID written in Crockford's Base32: a 48-bit millisecond timestamp followed by 80 random bits. Like UUID v7 it begins with a timestamp, but it's shorter to write and case-insensitive.
Can two UUIDs ever be the same?
In practice no. A v4 UUID has 122 random bits. You would need to generate about 2.7 × 10^18 of them for a 50% chance of a single duplicate.
How can I tell when a UUID was created?
Paste it into Inspect an ID. For v1, v6 and v7 UUIDs and for ULIDs the creation time is shown (with the node for v1 and v6). v4 (random) and v3 and v5 (name-based) UUIDs carry no timestamp. To convert the Unix milliseconds it shows, use the timestamp converter.
Can it make v3 or v5 name-based UUIDs?
No. It generates v4 and v7 UUIDs, ULIDs and NanoIDs. The inspector recognises v3 and v5 UUIDs when you paste one. They are built from an MD5 or SHA-1 hash of a namespace and a name; see the hash generator for those algorithms.
UUID versions compared
A UUID is 128 bits written as 32 hex digits in groups of 8-4-4-4-12. The first digit of the third group is the version. RFC 9562 (2024) replaced RFC 4122 and added versions 6, 7 and 8.
| Type | Built from | Sorts by time | Generated here |
|---|---|---|---|
| UUID v1 | Timestamp and node (often a MAC address) | No, the time fields are out of order | Inspect only |
| UUID v3, v5 | MD5 or SHA-1 hash of a namespace and name | No | Inspect only |
| UUID v4 | 122 random bits | No | Yes |
| UUID v6 | v1 reordered so the time comes first | Yes | Inspect only |
| UUID v7 | 48-bit Unix milliseconds and 74 random bits | Yes | Yes |
| ULID | 48-bit Unix milliseconds and 80 random bits, 26 characters | Yes | Yes |
| NanoID | Random characters from a URL-safe alphabet | No | Yes, any length from 4 to 64 |
Collision odds
With 122 random bits, the birthday bound puts a 50% chance of one duplicate at about 2.7 × 10^18 v4 UUIDs, or generating a billion a second for 85 years. A 21-character NanoID with the default 64-character alphabet has 126 random bits, similar to a v4 UUID. Shorter NanoIDs collide much sooner, so keep the default length unless your IDs are few.
Within the same millisecond, v7 UUIDs and ULIDs made here count up instead of re-rolling, so they stay in order even when you generate hundreds at once.