UUID Generator: Generate, Validate, and Copy UUIDs Instantly in Your Browser
A free tool to generate cryptographically random UUID v4 identifiers, validate any UUID string, and bulk-generate up to 100 UUIDs at once — no signup, no backend, fully client-side.
UUID Generator: Generate, Validate, and Copy UUIDs Instantly in Your Browser
We just shipped UUID Generator — a free browser-based tool for generating cryptographically random UUID v4 identifiers, validating UUID strings, and exporting in multiple formats. No account. No backend. Open the page and start generating.
What Is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. Written as 32 hexadecimal digits grouped into five segments:
550e8400-e29b-41d4-a716-446655440000
With roughly 2¹²² possible values for UUID v4, the probability of generating the same UUID twice is so small it's effectively zero for any real-world application.
UUIDs appear everywhere in software: database primary keys, session tokens, API request IDs, S3 object keys, idempotency tokens, distributed system message IDs, and configuration values. Developers need them constantly.
Why Does a UUID Generator Need to Exist?
The existing options are frustrating:
Search engines return ad-heavy results that generate one UUID at a time, can't validate inputs, and don't support format options.
Throwaway scripts work but require a terminal, a runtime, and a context switch:
import uuid
for _ in range(20):
print(uuid.uuid4())IDE plugins are convenient inside the editor but unavailable when reviewing code on a tablet, working on a colleague's machine, or needing a UUID from a browser-only environment.
UUID Generator is the tool developers actually need: fast, flexible, browser-native, and private.
How Does the UUID Generator Work?
How do I generate a UUID v4?
Click the Generate button on the Generate tab. Select a quantity first (1, 5, 10, 25, 50, or 100), pick a format, then click Generate. The tool uses crypto.randomUUID() — the browser's built-in cryptographically secure random number generator.
Is this UUID generator cryptographically secure?
Yes. The tool uses crypto.randomUUID() where supported, with a crypto.getRandomValues() polyfill as a fallback. Both use the operating system's CSPRNG — the same entropy source used by your operating system's /dev/urandom. This makes generated UUIDs suitable for security-sensitive contexts like session tokens and idempotency keys.
Math.random() is deliberately not used — it is not cryptographically secure and should never generate identifiers that need to be unguessable.
What UUID formats are supported?
Four formats:
| Format | Example |
|--------|---------|
| Standard (lowercase with hyphens) | 550e8400-e29b-41d4-a716-446655440000 |
| Compact (no hyphens) | 550e8400e29b41d4a716446655440000 |
| Uppercase (with hyphens) | 550E8400-E29B-41D4-A716-446655440000 |
| Uppercase compact | 550E8400E29B41D4A716446655440000 |
A live preview shows a sample UUID in the selected format before you click Generate.
How many UUIDs can I generate at once?
Up to 100 in a single click. Supported quantities: 1, 5, 10, 25, 50, 100. Each result appears in a list with individual copy buttons. A "Copy All" button copies the full batch newline-separated — ready to paste into a seed script, .env file, or test fixture.
How do I validate a UUID?
Switch to the Validate tab and paste any UUID string. The tool accepts:
- Standard format (with hyphens)
- Compact format (no hyphens)
- GUID format with surrounding braces (
{550e8400-...}) - Any combination of uppercase and lowercase
The validator returns: valid/invalid verdict, the UUID version (v1 through v7 where detectable), and the UUID normalized in all three formats.
When Would I Use a UUID Generator?
Database seeding and migrations
UUID v4 is the standard primary key format for PostgreSQL (UUID type), MySQL (CHAR(36) or BINARY(16)), and most ORMs (Prisma, TypeORM, Drizzle). When writing a seed script or migration, generate a batch of UUIDs here and paste them directly.
API testing
Need to test an endpoint that expects a UUID in the path (/users/{id}/settings) or request body? Grab one from the generator in seconds. Need 50 unique IDs for a load test? Bulk-generate and copy all.
Debugging logs
A UUID in a production log looks truncated or malformed. Paste it into the Validate tab to confirm whether it's actually invalid or just stored in compact format without hyphens.
Configuration values
Client IDs, webhook signing secrets, internal service tokens, and correlation IDs are often UUID-shaped. Generate them directly in the browser when setting up new environments.
Documentation examples
When writing API documentation, examples look more credible with realistic-looking UUIDs. Generate a set that matches the format your API actually returns.
What Is the Difference Between a UUID and a GUID?
A GUID (Globally Unique Identifier) is Microsoft's term for UUID. The underlying standard is identical (RFC 4122). The practical differences are cosmetic: GUIDs are often written in uppercase with surrounding curly braces, while UUIDs are written in lowercase without braces.
The UUID Generator's Validate tab accepts both GUID and UUID formats.
What Is the Difference Between UUID v4 and Other UUID Versions?
| Version | Generation method | Common use | |---------|------------------|-----------| | v1 | Timestamp + MAC address | Time-ordered IDs, distributed systems | | v3 | MD5 hash of namespace + name | Deterministic IDs from known inputs | | v4 | Random (CSPRNG) | General-purpose unique IDs | | v5 | SHA-1 hash of namespace + name | Deterministic IDs (preferred over v3) | | v6 | Reordered timestamp | Sortable, time-ordered IDs | | v7 | Unix timestamp + random bits | Sortable, database-friendly |
UUID v4 is the most widely used for general-purpose unique identifiers because it requires no coordination, has no privacy implications (unlike v1's MAC address embedding), and is supported natively in all modern languages and databases.
Does Storing UUIDs Hurt Database Performance?
UUID v4 has a known trade-off with database indexes: random bit patterns cause index fragmentation on B-tree indexes in databases like MySQL's InnoDB. This becomes measurable at scale (millions of rows).
Mitigations:
- PostgreSQL: Use the native
UUIDtype — its index implementation handles random UUIDs efficiently - MySQL/MariaDB: Store as
BINARY(16)instead ofCHAR(36)to reduce storage and improve cache efficiency; consider UUID v7 for insert-ordered workloads - General: The fragmentation concern only appears at significant scale — for most applications, UUID v4 as a primary key is fine
Can I Use UUID v4 as a Session Token?
UUID v4 is cryptographically random with 122 bits of entropy, making it suitable for session tokens if generated securely. The UUID Generator uses crypto.randomUUID() which meets this bar.
That said, purpose-built token generators (like crypto.randomBytes(32).toString('hex') in Node.js or secrets.token_urlsafe(32) in Python) produce tokens that are longer (256 bits) and are designed specifically for the token use case. For high-security session tokens, prefer a dedicated generator over UUID v4.
Technical Details
UUID Generator is built with Next.js 16, TypeScript, Tailwind CSS v4, and shadcn/ui. All logic runs client-side — no API calls, no analytics on your generated UUIDs, nothing sent to any server. The source code is available on GitHub.
