How to Generate a Batch of UUIDs for a Database Seed or Test Fixture

Here's the actual process for getting a real batch of version-4 UUIDs out of UUID generator, whether you need one for a quick test or a thousand for a seed file.

Step 1 - the page already has a real batch

Load the page and five valid v4 UUIDs are already sitting there - there's nothing to configure before you see real output. Click Generate any time for a completely fresh batch of the same count.

Step 2 - set how many you need

The Count field takes any value from 1 to 1,000. For a single ID, leave it at the default. For a seed file or a spreadsheet column, set it to whatever the job needs and click Generate once - all 1,000, if you use the maximum, come back in one batch, not one at a time.

Step 3 - pick a format

Three independent options, and none of them touch the actual randomness - they're a pure formatting pass applied after generation: Case (lowercase, the RFC 4122 convention, or UPPERCASE), Hyphens (the standard 8-4-4-4-12 grouping, or one continuous string), and a Wrap in braces checkbox for the {...} form some older Windows APIs and COM interfaces still expect. Changing any of these re-renders the same underlying batch instantly - it never generates new values, so you can switch formats after the fact without losing the specific IDs you already have.

Step 4 - copy or download

Copy all puts the exact visible list on your clipboard, one UUID per line. Download .txt saves the same list as a plain text file, ready to pipe into a seed script or paste into a spreadsheet column.

Where the randomness actually comes from

Every UUID is generated with crypto.randomUUID() where the browser supports it, or built by hand from 16 bytes out of crypto.getRandomValues() on slightly older browsers - both draw from the Web Crypto API's cryptographically secure random number generator, the same source browsers use for things like session tokens. This tool never falls back to Math.random(), which is not cryptographically secure and is a meaningfully weaker guarantee than what a UUID's format implies. If neither Web Crypto function exists in your browser at all, the tool says so plainly rather than silently generating weaker IDs.

If the Count field ends up empty or invalid

Typing into a number input, deleting the value entirely, or briefly leaving something non-numeric while editing never crashes the tool or clears your batch - the last valid count simply stays in effect until you enter a new one the browser accepts. There's no error state to hit here by accident.

Nothing about this ever leaves your browser

There's no upload step to describe, because there's no input to upload in the first place - the Count and format options are the only things you set, and every UUID is generated and formatted locally. Nothing is sent to a server before, during, or after you click Generate, which also means there's no network round trip slowing anything down, even at the full 1,000-UUID batch size.

If a value looks wrong

Every UUID this tool produces is version 4 specifically - the general-purpose random kind, not the time-based (v1) or namespace-hashed (v3/v5) variants. If you need a different version for a specific integration's requirements, this isn't that tool; it's scoped to v4 on purpose, which is what almost every practical use case - a database key, a test fixture, an idempotency key - actually needs.

A second reason to reach for a big batch

Seeding a single table is the obvious use, but a large batch is just as useful for keeping test data distinct across parallel CI runs, so two runs hitting the same database schema at once never accidentally collide on a fixture's ID. Generate a batch once, download it as a .txt file, and check it into your test fixtures directory - a real, versioned list beats regenerating random values inline in a test and hoping nothing ever repeats.

What this tool doesn't do

It generates standard 36-character UUIDs (32 hex digits plus hyphens, or without them) - not a shorter custom ID scheme, not a Base62 or NanoID-style compact identifier. If your project specifically wants a shorter, URL-friendlier random ID rather than an RFC 4122 UUID, that's a different, narrower format this tool isn't trying to produce; it stays scoped to a real, standards-compliant UUID.

Uses beyond a database row

A database primary key is the obvious use, but a v4 UUID is just as useful anywhere you need a guaranteed-unique token with no meaning attached to it: an idempotency key sent with an API request so a retried call is recognized as the same request rather than a duplicate, a temporary filename that won't collide with anything else in a shared upload directory, or a placeholder value in a config file or test fixture standing in for "some ID, doesn't matter which." None of these need the value to be sortable - they need it to be safely unique, which is exactly what this tool guarantees.

For why v4's randomness means no built-in ordering, and when that matters for a database primary key, see the background. Or generate a batch now.