UUID Generator
Generate cryptographically random UUID v4 values instantly in your browser — pick how many you need and copy or download the list.
What Is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit value, usually written as 32 hex characters split into five groups, like f47ac10b-58cc-4372-a567-0e02b2c3d479. It's designed so that generating one anywhere, at any time, is astronomically unlikely to collide with any other UUID ever generated — no central registry or coordination required.
This tool generates version 4 UUIDs, the most common variant: every UUID is built from a cryptographically random number generator, not derived from a timestamp or hardware identifier.
Why Use UUIDs?
Auto-incrementing integer IDs (1, 2, 3, ...) are simple but reveal how many records exist, are easy to guess, and collide instantly if you ever merge data from two separate sources. A UUID sidesteps all three problems: it's unguessable, doesn't leak volume information, and can be generated independently by any number of systems without ever needing to check in with each other.
How This Tool Works
Type how many UUIDs you want (1 to 100) and click Generate. Each one is created with your browser's built-in cryptographically secure random number generator (crypto.randomUUID()) — the same standard used by databases and programming languages. Nothing is uploaded to any server; the values never leave your browser.
Auto-Increment IDs vs. UUIDs
| Feature | Auto-Increment Integer | UUID v4 |
|---|---|---|
| Uniqueness guarantee | Only within one database/table | Effectively global |
| Generated by multiple systems independently | Collides immediately | Safe |
| Predictable/guessable | Yes (1, 2, 3, ...) | No |
| Reveals record count | Yes | No |
| Storage size | Small (4-8 bytes) | Larger (16 bytes / 36-character string) |
| Human-typable | Easy | Awkward |
Use Auto-Increment IDs When
- Everything lives in a single database and you control ID assignment centrally
- Storage size and index performance matter more than unguessability
- You want IDs a person can easily read, type, or say out loud
Use UUIDs When
- IDs need to be generated by multiple services, offline clients, or before a record is even saved to a database
- You don't want an ID to reveal how many records exist or make the next one guessable
- You're merging data from multiple sources and need to guarantee no collisions
Common Scenarios for Generating UUIDs
Naming Uploaded Files Without Collisions
When users upload files — photos, documents, attachments — naming each one with a UUID instead of its original filename avoids collisions between two people uploading a file called photo.jpg. This matters even more when processing a whole batch at once, like renaming a set of images before running them through our Bulk Image Compressor.
Assigning a Primary Key Before Saving to a Database
Some architectures need an ID assigned before a record is inserted (for example, to reference it in a related record within the same transaction). Generating a UUID client-side or in application code, rather than waiting on an auto-increment value from the database, makes that possible.
Creating a Unique Session or Request ID
Tracing a single request through logs across multiple services is much easier when every log line is tagged with the same UUID, generated once at the start of the request.
Seeding Test or Placeholder Data
When writing tests or building a demo dataset, UUIDs give you realistic-looking unique identifiers without worrying about accidentally reusing a real ID from production data.
Generating API Keys or One-Time Tokens
A UUID's unguessability makes it a reasonable building block for a one-time token or a simple API key, though for anything security-sensitive you'll want to pair it with proper hashing and expiration logic in your backend.
Other Ways to Generate a UUID
You can also generate a UUID using your command line (uuidgen on Mac/Linux, or [guid]::NewGuid() in PowerShell), or a one-line snippet in most programming languages' standard library. FileCast is useful when you need several at once without opening a terminal.
Frequently Asked Questions
Are these UUIDs actually unique?
Practically, yes. A version 4 UUID has 122 random bits, giving roughly 5.3 undecillion possible values. Even generating billions of UUIDs per second, the chance of ever producing a duplicate is negligible for virtually any real-world use case.
Is this safe to use for security purposes, like session tokens?
The randomness itself is safe — crypto.randomUUID() uses your browser's cryptographically secure random number generator, not a weak pseudo-random one. That said, a UUID alone isn't a full security solution: for authentication tokens, pair it with proper expiration, hashing, and server-side validation.
Are the UUIDs generated on a server?
No. Every UUID is generated locally in your browser using the Web Crypto API. Nothing is sent anywhere, and this tool has no way to log or see the values you generate.
What UUID version does this generate?
Version 4 — the randomly-generated variant, and the most commonly used one. It doesn't encode a timestamp, MAC address, or any other identifying information, unlike some other UUID versions.
How many can I generate at once?
Up to 100 per click. For more, just click Generate again and combine the results, or download each batch as a text file.