How are the UUIDs generated?

UUID v4 values come from the browser native crypto.randomUUID() function, which draws on the operating system cryptographically secure random source. If that function is missing, the tool falls back to crypto.getRandomValues() and sets the version and variant bits by hand, so the result is still a valid, cryptographically random RFC 4122 identifier.

What is the difference between a UUID and a ULID?

A v4 UUID is 128 bits of pure randomness, so two of them never collide in practice but they sort in random order. A ULID packs a 48-bit millisecond timestamp followed by 80 random bits and encodes the whole thing in Crockford base32, so ULIDs sort lexicographically by creation time, which is handy for database keys and log lines.

How many identifiers can I generate at once?

Up to 5,000 in a single batch. Generation is instant because everything happens locally in your browser, with no round trips to a server, so even the largest batch appears immediately and downloads as a single file.

Are the generated IDs unique?

For practical purposes, yes. The odds of a v4 UUID collision are astronomically small even across billions of values, and ULIDs combine a timestamp with 80 random bits per identifier. This tool also advances the ULID timestamp across a batch so a large run made in the same millisecond stays in sorted order.

Can I download the list as CSV or JSON?

Yes. Use the .csv button for a single-column file with a header row, the .json button for a JSON array of strings, or .txt for one identifier per line. The file name includes the format and the count so batches stay organised in your downloads folder.

Is anything sent to a server?

No. The generator is 100% client-side. The identifiers, your formatting options and the recent-batch history all stay in your browser local storage and are never uploaded, which makes the tool safe to use for production keys and offline work.

UUID / ULID Batch Generator

A batch generator for v4 UUIDs and ULIDs that produces up to 5,000 unique identifiers in a single click, with full control over case, hyphens, prefixes, quoting and export format. It is built for developers seeding databases, writing fixtures and test data, populating spreadsheets, or generating a column of keys to paste into code — anywhere you need many random identifiers at once instead of copying them one at a time.

How it works

Every value is created locally in your browser. For UUID v4 the tool calls the native crypto.randomUUID() function, which is backed by the operating system’s cryptographically secure random source; if that function is unavailable it falls back to crypto.getRandomValues() and sets the version and variant bits manually so the output is still a valid RFC 4122 identifier. For ULID it encodes a 48-bit millisecond timestamp into the first ten Crockford base32 characters and 80 bits of fresh randomness into the remaining sixteen, giving an identifier that sorts by creation time. Across a large batch the timestamp is advanced by one millisecond per row, so the whole list stays monotonic and readable even when generated in the same instant.

Once the batch is built you can reshape it without regenerating: toggle lowercase or uppercase, strip the hyphens from UUIDs for compact tokens, add a prefix like user_ or a suffix like .json, wrap each value in quotes, or switch to comma-separated lines for dropping straight into an array literal. Settings and your last twelve batches are remembered in localStorage, and nothing is ever transmitted — making it safe for production keys.

Example

Suppose you need 100 database row IDs that sort by insertion time. Choose ULID, set the count to 100, leave the case as uppercase (the ULID canonical form), and press Generate. You get a sorted column such as 01HZX8P9QK6F3R2WB7N4M5T0AD repeated 100 times with distinct random tails. Hit the .csv button and you have a ready-to-import file. Need quoted JavaScript literals instead? Tick Wrap in quotes and Comma-separated lines, then Copy all, and paste a complete array into your code.

Format	Length	Sorts by time	Typical use
UUID v4	36 chars	No	General-purpose unique keys
ULID	26 chars	Yes	Database primary keys, log IDs
Nil UUID	36 chars	n/a	Placeholder / “no value” sentinel
GUID `{braces}`	38 chars	No	Windows registry / .NET interop

Every identifier is generated in your browser — nothing is uploaded or stored on a server.