UUID Generator

Generate random UUID v4 identifiers instantly. Cryptographically secure, browser-based, and free.

Free to use. Runs in your browser.

UUID v4 uses 122 random bits for virtually collision-free unique identifiers.

Generate one identifier for a record, or create a batch for fixtures, migrations, and API examples.

Count

Format

Standard format

Use hyphenated lowercase UUIDs for most APIs and databases: 8-4-4-4-12 hex characters.

Bulk batches

Batch generation is useful for seed data, test fixtures, and spreadsheet imports where every row needs its own identifier.

Security boundary

UUIDs identify resources. Use a separate cryptographic token for passwords, API keys, sessions, and one-time links.

Database note

PostgreSQL has a native UUID column type. Storing UUIDs as text works, but it uses more space and compares more slowly.

What Is a UUID and When Should You Use One?

A UUID (Universally Unique Identifier) is a 128-bit number formatted as 32 hexadecimal digits in five groups: 550e8400-e29b-41d4-a716-446655440000. The key property: any two UUIDs generated anywhere in the world at any time are virtually guaranteed to be different. No coordination needed.

A v4 UUID has 122 random bits (version and variant bits are fixed), giving 2¹²² possible values — roughly 5.3 × 10³⁶. You would need to generate about 103 trillion UUIDs before the probability of any collision reaches one in a billion. That is why databases, distributed systems, and APIs use them as primary keys without central coordination.

This generator creates v4 UUIDs (random), the most common type. Each one is generated using your browser's cryptographic random number generator, so they're suitable for production use. Generate one or many, copy, and paste into your code.

UUID Versions Compared

Version	Based On	When to Use
v1	Timestamp + MAC address	When you need time-ordering and traceability (leaks MAC address)
v3	MD5 hash of namespace + name	Deterministic IDs from known input (use v5 instead, MD5 is weak)
v4	Random numbers	General purpose, most common. This is what this tool generates
v5	SHA-1 hash of namespace + name	Deterministic IDs where same input always gives same UUID
v7 (new)	Timestamp + random	Sortable by time, better database index performance than v4

What this means for you: Use v4 for general-purpose IDs. If you need sortable, time-ordered IDs (better for database performance), consider v7 UUIDs or ULID. If you need deterministic IDs (same input → same UUID), use v5.

UUID vs Other ID Formats

Format	Length	Sortable	Best For
UUID v4	36 chars	No	General-purpose unique IDs
UUID v7	36 chars	Yes (by time)	Database primary keys
ULID	26 chars	Yes (by time)	Compact, sortable alternative to UUID
NanoID	21 chars (default)	No	URL-safe, compact IDs
Auto-increment	Variable	Yes	Single-database systems (leaks count)
Snowflake ID	18-19 digits	Yes (by time)	Distributed systems (Twitter, Discord)

UUID Practical Considerations

Database performance

Random v4 UUIDs cause index fragmentation in B-tree databases (PostgreSQL, MySQL). v7 UUIDs or ULIDs are time-ordered, so inserts are sequential and indexes stay efficient. Use v7 for high-write databases.

Storage format

Store UUIDs as native UUID type (16 bytes) in PostgreSQL, not VARCHAR(36). The text format with hyphens takes 36 bytes plus overhead. Binary storage is 2x smaller and compares faster.

Don't expose sequential IDs

Auto-increment IDs (user/1, user/2, user/3) leak information: how many users you have, when they signed up, and make it trivial to enumerate resources. UUIDs hide this.

UUIDs aren't secrets

UUIDs are unguessable but not secret. Don't use a UUID as an authentication token or session key. An attacker who intercepts a UUID can reuse it. Use proper cryptographic tokens for security.

Generating UUIDs in Code

Language	Code
JavaScript	crypto.randomUUID()
Python	import uuid; str(uuid.uuid4())
PostgreSQL	gen_random_uuid()
Ruby	SecureRandom.uuid
Go	uuid.New() // google/uuid
CLI (Linux/Mac)	uuidgen

JavaScript's crypto.randomUUID() is available in current browsers and Node.js 19+. No library needed, it's built in.

Choosing a UUID Format

UUIDs are the same 128-bit value whether they are shown with hyphens, without hyphens, in uppercase, or inside braces. Format choice is usually about the system you are pasting into.

If a system accepts more than one format, standard lowercase with hyphens is the least surprising choice for logs, API examples, and support tickets.

Format	Example	Use It For
Standard	550e8400-e29b-41d4-a716-446655440000	APIs, PostgreSQL UUID columns, logs, documentation
No hyphens	550e8400e29b41d4a716446655440000	Systems that store compact hex strings
Uppercase	550E8400-E29B-41D4-A716-446655440000	Older systems or style guides that require uppercase hex
Braces	{550e8400-e29b-41d4-a716-446655440000}	Windows registry, COM, and some configuration files

Collision Risk in Plain English

A v4 UUID has 122 random bits after reserving version and variant bits. That is enough space that accidental collisions are not the practical risk for most applications. Bad generation methods, copying the same ID twice, or using UUIDs where secrets are needed are more common problems.

Good use

Creating identifiers independently across services, queues, local-first apps, migration scripts, and offline devices.

Poor use

Replacing session tokens, API keys, password reset links, or anything that needs expiry, revocation, and deliberate secret handling.

Real risk

Duplicating rows during imports, seeding fixtures without regenerating IDs, or using a weak random source in old code.

Practical guardrail

Keep a unique constraint on the database column. The constraint should never fire in normal use, but it protects data if a workflow goes wrong.

Database and API Notes

Context	Recommendation	Reason
PostgreSQL	Use the native uuid type	Stores 16 bytes and validates the format
MySQL	Consider BINARY(16) for large tables	Smaller than storing 36-character text
REST APIs	Keep standard hyphenated strings	Human readable and widely accepted by clients
URLs	Use lowercase standard form unless a system says otherwise	Lowercase avoids duplicate-looking representations
High-write tables	Evaluate UUID v7 or ULID	Time ordering reduces random index inserts

Bulk Generation Checklist

Fixtures and seed data

Generate stable IDs only when tests depend on specific relationships. For throwaway fixtures, regenerate IDs so copied data does not collide.

Spreadsheet imports

Add one UUID per row before import if the destination system does not create IDs for you. Keep the column as text in the spreadsheet so hyphens are preserved.

Logging and tracing

A UUID can label one request, job, or transaction across several log lines. Use a different field for user IDs so trace IDs do not become business identifiers.

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How to use this tool

Choose the number of UUIDs to generate

Click Generate to create new UUIDs instantly

Copy individual UUIDs or all at once

Common uses

Generating unique database primary keys
Creating unique identifiers for API resources
Assigning session or transaction IDs
Producing unique file names to prevent collisions

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Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit number formatted as 32 hex digits in five groups: 550e8400-e29b-41d4-a716-446655440000. Any two UUIDs generated anywhere are virtually guaranteed to be different, no coordination needed.

Are UUIDs truly unique?

UUID v4 uses 122 random bits, giving about 5.3 × 10³⁶ possible values. You would need to generate roughly 103 trillion UUIDs before the probability of any collision reaches one in a billion. In practice, collisions are not the risk for most applications — bad generation code, copied IDs, or weak random sources are far more common problems.

Is this generated server-side?

No. UUIDs are generated entirely in your browser using crypto.randomUUID(), the Web Crypto API's built-in UUID generator. It uses cryptographically secure randomness, making these suitable for production use.

What format options are available?

Standard (with hyphens: 550e8400-e29b-41d4-...), no hyphens (550e8400e29b41d4...), uppercase (550E8400-E29B-...), and braces format ({550e8400-e29b-...}). The braces format is used in Windows/COM programming.

What's the difference between UUID v4 and v7?

v4 is purely random. v7 encodes a timestamp in the first 48 bits plus random data, making it time-sortable. v7 is better for database primary keys because sequential inserts are more efficient for B-tree indexes. This tool generates v4.

Should I use UUIDs as database primary keys?

v4 UUIDs work but cause index fragmentation in B-tree databases (PostgreSQL, MySQL) because random values scatter inserts. Consider v7 UUIDs or ULIDs for high-write databases, they're time-ordered, so inserts are sequential.

How do I store UUIDs efficiently in a database?

Use the native UUID type in PostgreSQL (16 bytes). In MySQL, use BINARY(16) with UUID_TO_BIN(). Don't store as VARCHAR(36), it wastes space (36 bytes + overhead vs 16 bytes) and compares slower.

What's the difference between UUID and GUID?

Nothing, they're the same thing. UUID is the IETF standard name. GUID (Globally Unique Identifier) is Microsoft's name for the same format. Both are 128-bit identifiers formatted identically.

Can I generate UUIDs in my code?

JavaScript: crypto.randomUUID(). Python: import uuid; uuid.uuid4(). Java: UUID.randomUUID(). Go: uuid.New() (google/uuid package). PHP: Ramsey\Uuid\Uuid::uuid4(). All produce standard v4 UUIDs.

Are UUIDs secure enough for tokens?

UUIDs are unguessable but not secret. They're fine for resource identifiers but shouldn't be used as authentication tokens or API keys. An attacker who intercepts a UUID can reuse it. Use proper cryptographic tokens (like those from crypto.randomBytes) for security.

What's a ULID and how does it compare?

A ULID (Universally Unique Lexicographically Sortable Identifier) is 26 characters (vs UUID's 36), time-sortable, and URL-safe. It's a compact alternative to UUID v4. If you need sortability and compactness, ULID is worth considering.

Can I generate UUIDs in bulk?

Yes, set the count to up to 100 and click Generate. All UUIDs are created instantly. Copy them all at once or generate more batches as needed.

Results are for general informational purposes only and should be checked before use. They are not professional advice. See our Disclaimer and Terms of Service.