UUID / ULID Generator
Bulk-generate UUID v4, UUID v7 and ULID identifiers. Runs in your browser.
About this uuid / ulid generator
This generator creates UUID v4, UUID v7 and ULID identifiers, from a single ID to 1,000 at once. Copy one with a click, copy the whole list, or download it as a text file, a JSON array or a ready-to-paste SQL list.
It is for developers who need IDs for database rows, test fixtures, config entries or API requests. UUID v4 is fully random. UUID v7 and ULID start with a timestamp, so they sort by creation time, which keeps database indexes fast. IDs made in the same millisecond still come out in order.
All randomness comes from your browser's cryptographic random number generator, and nothing is requested from a server. You can also paste any UUID or ULID to see its version and, for time-based IDs, when it was created.
Features
UUID v4, UUID v7 and ULID
Three ID types on one page. v4 uses the browser's crypto.randomUUID, v7 follows RFC 9562, and ULID uses Crockford base32.
Sorted even within one millisecond
UUID v7 uses a 12-bit counter and ULID increments its random part when several IDs share a millisecond, so a bulk list is always in creation order.
Bulk generation up to 1,000
Enter any number from 1 to 1,000. Click a single ID in the list to copy just that one, or copy and download them all.
Formats for your code
Uppercase, with or without hyphens, and with braces for .NET-style GUIDs. Export one per line, as a JSON array, or as a quoted SQL list.
ID inspector
Paste a UUID, GUID or ULID to see its type, version and variant, plus the embedded timestamp for UUID v1, v6, v7 and ULID.
Cryptographic randomness
Every random bit comes from crypto.getRandomValues or crypto.randomUUID. Math.random is never used.
How to use the uuid / ulid generator
- 1Pick UUID v4, v7 or ULID and how many (1 to 1,000).
- 2Choose a format, then Generate new or Ctrl+Enter.
- 3Copy one, copy all, or download.
When to use it
Database primary keys
Generate UUID v7 or ULID keys that sort by time, so new rows land at the end of the index.
Test data and fixtures
Create 100 IDs as a JSON array and paste them straight into a test file or seed script.
SQL scripts
Export a quoted, comma-separated list to use in an INSERT statement or a WHERE id IN (…) clause.
Windows and .NET GUIDs
Generate uppercase GUIDs in braces for registry entries, project files and COM components.
Checking an unknown ID
Paste an ID from a log or database to find out which version it is and when a time-based ID was created.
UUID v4 vs v7 vs ULID
All three are 128-bit identifiers that you can create anywhere without asking a central server. The chance of two random ones colliding is so small that you can ignore it in practice. They differ in what the bits contain and how they sort.
- UUID v4: 122 random bits. Reveals nothing about when or where it was made. Random order, which scatters inserts across a database index.
- UUID v7: a 48-bit Unix timestamp in milliseconds, then counter and random bits. Same 36-character format as v4, so it fits any UUID column, but it sorts by creation time.
- ULID: the same idea as v7, a 48-bit timestamp plus 80 random bits, written as 26 characters of Crockford base32. Shorter, URL-safe, case-insensitive, and it avoids the letters I, L, O and U.
Which one should you use?
For new database primary keys, use UUID v7. Time-ordered keys keep B-tree indexes compact and inserts fast, and the format works with existing UUID column types in PostgreSQL, MySQL and SQL Server.
Use UUID v4 when an ID must not reveal when it was created, such as a public token or an invitation link. Use ULID when you want a shorter, sortable string, for example in URLs or file names, and your system does not require the UUID format.
How a UUID is structured
A UUID is written as 32 hexadecimal digits in five groups: 8-4-4-4-12. The first digit of the third group is the version, so a v4 UUID always has a 4 there and a v7 UUID a 7. The first digit of the fourth group shows the variant. For standard UUIDs it is 8, 9, a or b.
In a v7 UUID, the first 12 hex digits are the creation time in milliseconds since 1970. That is how the inspector can show when a v7 UUID was made.
Why use Mavros
| Mavros | Typical upload sites | |
|---|---|---|
| Where IDs are made | In your browser | Sometimes fetched from a server |
| Randomness source | Cryptographic (crypto.getRandomValues) | Not always stated |
| UUID v7 order in bulk | Strictly sorted, even within one millisecond | Often unsorted within a millisecond |
| UUID and ULID on one page | Yes, plus an inspector | Usually separate sites |
| Export formats | Lines, JSON array, SQL list | Plain list |
Tips
- Press Ctrl+Enter (Cmd+Enter on a Mac) to generate a new batch.
- Store UUIDs in a native UUID or 16-byte binary column, not as text, to save space and speed up lookups.
- Do not use UUID v7 or ULID as secret tokens. Their timestamp is readable and part of the value is predictable.
- Use the SQL list format to paste IDs straight into an IN (…) clause.
- Most systems treat UUIDs as case-insensitive, but lowercase is the standard form. Keep one style across your project.
Questions
What is a UUID?
A UUID (universally unique identifier) is a 128-bit value written as 36 characters, such as 550e8400-e29b-41d4-a716-446655440000. Systems create them independently and can still treat them as unique.
Is a GUID the same as a UUID?
Yes. GUID is Microsoft's name for a UUID. Windows tools often show GUIDs in uppercase and in braces, which you can switch on here.
Should I use UUID v4 or v7?
Use v7 for database primary keys: it is sortable by creation time, which keeps indexes fast. Use v4 when IDs must not reveal when they were created.
Can two UUIDs ever be the same?
In theory yes, in practice no. A v4 UUID has 122 random bits. You would need to generate about a billion per second for decades before a single collision became likely.
What is a ULID?
A ULID is a 26-character ID made of a millisecond timestamp and 80 random bits, written in Crockford base32. It sorts by creation time and is shorter than a UUID.
Are these IDs secure enough for tokens?
They come from a cryptographic random generator. UUID v4 has 122 random bits and works as an unguessable token. v7 and ULID reveal their creation time, so do not use them as secrets.
How many UUIDs can I generate at once?
Up to 1,000 per batch. Copy them all or download them as a text or JSON file.
Can I find out when a UUID was created?
Yes, for time-based IDs. Paste a UUID v1, v6, v7 or a ULID into the inspector to see its timestamp. A v4 UUID contains no time information.