About the UUID / ULID Generator
How it works and when to use each identifier format.
What it is
The UUID / ULID Generator is a free, browser-based tool that generates unique identifiers in three formats — UUID v4, UUID v7, and ULID — in batches of up to 100. All generation runs entirely client-side using the Web Crypto API, so no IDs are ever sent to a server. Choose a format, set a count, pick uppercase or lowercase, click Generate, then copy individual IDs or the full batch with one click.
The three formats
UUID v4 (random)
122 random bits from a cryptographically secure source. The most widely supported UUID format — works with every database, framework, and language. Looks like: 550e8400-e29b-41d4-a716-446655440000
UUID v7 (time-ordered)
A 48-bit Unix millisecond timestamp in the high bits followed by random bits. Monotonically increasing, B-tree-friendly — ideal as database primary keys because new rows always insert at the tail of the index.
ULID
Universally Unique Lexicographically Sortable Identifier. 48-bit timestamp + 80 random bits, encoded as 26 Crockford Base32 characters. URL-safe, human-readable, sorts by time. Example: 01ARZ3NDEKTSV4RRFFQ69G5FAV
Features
Bulk generation
Generate 1 to 100 unique IDs in a single click. Set the Count field to any number in that range.
Copy All
Copy the entire batch as a newline-separated list — paste directly into a migration script, seed file, or spreadsheet.
Individual copy
Each generated ID has its own Copy button for when you need just one value from a larger batch.
Uppercase / lowercase
Toggle hex output between UPPER and lower case for UUID formats. ULIDs are always uppercase Crockford Base32.
Web Crypto API
Uses crypto.randomUUID() for v4 and crypto.getRandomValues() for v7 and ULID — cryptographically secure randomness guaranteed by the browser.
Fully client-side
No server round-trips. Generated IDs never leave your browser, making this safe for seeding test databases with sensitive schemas.
Which format should I use?
Use UUID v4 when you need a universally compatible unique identifier and don't care about sort order — for session tokens, API keys, correlation IDs, or anywhere an existing system expects a standard UUID. Use UUID v7 when the ID is a primary key in a relational database — its time-ordered structure keeps B-tree indexes compact and insert performance high. Use ULID when you need time-sortable IDs that are also URL-safe and shorter to type or display — common in distributed systems where lexicographic ordering matters and you want something more compact than a UUID.