How to Generate UUID v4 Online — Free & Instant
To generate a UUID, simply open the tool and click the Generate button. A new UUID v4 — a 128-bit random identifier formatted as eight-four-four-four-twelve hexadecimal characters (e.g., 550e8400-e29b-41d4-a716-446655440000) — appears instantly in the output field. Click Copy to send it to your clipboard, ready to paste into your code, database, or configuration file.
To generate multiple UUIDs at once, use the quantity selector to choose how many you need (up to 100), then click Generate. All UUIDs appear in the output list. You can copy each one individually or use the Copy All button to grab the entire batch separated by newlines — useful when seeding databases, creating test fixtures, or assigning IDs to a batch of records.
Why Use This Free UUID v4 Generator?
- 100% browser-based — UUIDs are generated client-side using the Web Crypto API and never sent to any server
- Cryptographically random — each UUID v4 uses secure random bytes, not a predictable pseudo-random seed
- Bulk generation — create up to 100 unique UUIDs in one click for seeding databases or test fixtures
- One-click copy for each UUID or the entire batch at once
- No rate limits, no account, no installation — works on any device with a browser
- Standards-compliant RFC 4122 format guaranteed on every generation
- Works offline after page load — generate UUIDs without an internet connection
Frequently Asked Questions
What is a UUID and what is it used for?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122, typically displayed as 32 hexadecimal digits in five groups: 8-4-4-4-12 (e.g., 550e8400-e29b-41d4-a716-446655440000). UUIDs are used as unique keys in databases, identifiers for API resources, session tokens, file names, and anywhere you need a globally unique value without a central authority assigning IDs. They're especially useful in distributed systems where multiple servers need to generate IDs independently without coordination.
Source: RFC 4122 — A Universally Unique IDentifier (UUID) URN Namespace
What is the difference between UUID v1, v3, v4, and v5?
UUID v1 is generated from the current timestamp and the host machine's MAC address — making it sortable by time but potentially privacy-sensitive. UUID v3 is a deterministic hash (MD5) of a namespace and a name, so the same inputs always produce the same UUID. UUID v4 is purely random, using 122 random bits — the most commonly used version for general-purpose unique IDs. UUID v5 is like v3 but uses SHA-1 hashing. This tool generates UUID v4 because it's the safest, most private, and most universally supported option.
What are the chances of two UUIDs being the same?
UUID v4 collision probability is astronomically low. With 122 bits of randomness, you would need to generate approximately 2.71 quintillion UUIDs before reaching a 50% probability of a single collision. In practice, UUID collisions are treated as theoretically impossible — real systems have never recorded one. This makes UUID v4 safe to use as primary keys without a uniqueness check.
Can I use a UUID as a database primary key?
Yes, and it's a common pattern. UUID primary keys allow records to be created on the client before they're persisted to the database (useful in offline apps and distributed inserts), eliminate sequential ID enumeration attacks, and make it trivially easy to merge data from multiple sources. The trade-off is storage size (16 bytes vs 4–8 bytes for integer keys) and slightly reduced index performance on very large tables. For most applications the benefits outweigh the costs. If sort order matters, consider UUID v7 (time-ordered) for better index locality.
Is a UUID the same as a GUID?
Yes, GUID (Globally Unique Identifier) is Microsoft's name for the same concept — they are interchangeable. GUIDs are used extensively in Windows, .NET, COM, and Microsoft SQL Server. The format is identical to UUID (RFC 4122). Some systems display GUIDs with uppercase hex and surrounding braces {550E8400-E29B-41D4-A716-446655440000}, but the underlying value is the same.
What is UUID v7 and how does it differ from v4?
UUID v7, defined in RFC 9562 (published May 2024, superseding RFC 4122), embeds a Unix timestamp in the most significant 48 bits, followed by random bits for uniqueness. This makes v7 UUIDs time-sortable — they naturally sort in chronological order, which dramatically improves database index performance compared to fully random v4 UUIDs. UUID v7 is recommended for new systems where time-ordered IDs are beneficial (e.g., database primary keys, event logs, message queues). UUID v4 remains the best choice when you need IDs with no embedded metadata or when time-ordering is not required.
How do I generate a UUID in JavaScript, Python, Go, or other languages?
Most languages have built-in UUID generation. JavaScript (Node.js 14.17+): crypto.randomUUID() — returns a v4 UUID string natively without any library. Browser: crypto.randomUUID() is also available in modern browsers (this tool uses it). Python: import uuid; str(uuid.uuid4()). Go: use the google/uuid package — uuid.New().String(). Java: UUID.randomUUID().toString(). PHP: Ramsey\Uuid\Uuid::uuid4()->toString() (via the ramsey/uuid package) or use the built-in in Laravel. Ruby: SecureRandom.uuid. PostgreSQL: gen_random_uuid() (built-in since v13) or uuid_generate_v4() (via the uuid-ossp extension). All of these produce RFC 4122-compliant v4 UUIDs identical in format to what this generator produces.
How do I generate multiple UUIDs at once?
Use the quantity selector in this tool to set a count from 1 to 100, then click Generate. All UUIDs appear in the list and you can copy them all at once with the Copy All button, or download them as a .txt file. For generating large batches programmatically, use a loop: in JavaScript, Array.from({length: 1000}, () => crypto.randomUUID()) generates 1000 UUIDs in a single expression. In Python, [str(uuid.uuid4()) for _ in range(1000)] does the same. For millions of UUIDs, the command-line tool uuidgen (available on macOS and Linux) can be piped in a shell loop or used with tools like seq.
Can I use UUIDs as API keys or session tokens?
UUID v4s are technically suitable as session identifiers because they're randomly generated and unpredictable, but there are better options for API keys and tokens specifically. UUID v4 has 122 bits of randomness, which is secure enough, but they're encoded in hex format which is less compact than base64. A 32-byte (256-bit) cryptographically random value encoded in base64url is more entropy-efficient and is the standard format for API keys (used by AWS, Stripe, GitHub, etc.). For session tokens, JWTs or opaque random tokens are more common. UUIDs are best used as resource identifiers (database primary keys, record IDs) rather than credentials or secrets.
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