🔑 UUID / GUID Generator
What Is a UUID?
A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier) in Microsoft environments, is a 128-bit identifier designed to be unique across all devices and all time without requiring a central registration authority. The standard format is 32 hexadecimal digits displayed in five groups separated by hyphens: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx, where the 4 indicates version 4 (random) and y is one of 8, 9, a, or b.
The probability of generating two identical UUID v4 values is approximately 1 in 2122 — so small that for all practical purposes, every UUID you generate is guaranteed to be unique. You would need to generate 1 billion UUIDs per second for about 85 years before having a 50% chance of a single collision.
Example output
7c9e6679-7425-40de-944b-e07fc1f90ae7
550e8400-e29b-41d4-a716-446655440000
UUID Versions Compared
| Version | Based on | Use case |
|---|---|---|
| v1 | Timestamp + MAC address | Ordered IDs, but leaks hardware info |
| v3 | MD5 hash of namespace + name | Deterministic IDs from known inputs |
| v4 | Random / pseudo-random | General purpose — most common |
| v5 | SHA-1 hash of namespace + name | Like v3 but with stronger hash |
| v7 | Unix timestamp + random | Sortable by creation time (new standard) |
Common Use Cases
Database primary keys
UUIDs let you generate IDs on the client side without round-tripping to the database. This simplifies distributed architectures and offline-capable apps.
API request tracing
Assign a UUID to each API request for end-to-end tracing through microservices. Makes debugging distributed systems dramatically easier.
Session identifiers
Web frameworks use UUIDs for session tokens because their randomness makes them unpredictable and their length makes collisions impossible.
File and resource naming
When users upload files, renaming them with UUIDs prevents name collisions and hides the original filename for privacy.
Message queue deduplication
In message brokers like Kafka or RabbitMQ, UUIDs serve as idempotency keys to prevent duplicate message processing.
Test data seeding
Need 1,000 unique IDs for a database seed script? Batch-generate them here and paste directly into your SQL or JSON fixtures.
UUIDs vs Auto-Increment IDs
Traditional auto-incrementing integer IDs (1, 2, 3...) are simple but reveal information: competitors can estimate your user count, attackers can enumerate records, and merging databases from different servers causes ID conflicts. UUIDs solve all three problems at the cost of being larger (16 bytes vs 4–8 bytes) and not naturally sorted. For most modern applications, the trade-off is worth it.
Frequently Asked Questions
Theoretically yes, but practically no. With 122 random bits, the chance of collision is about 1 in 5.3 × 1036. You’re more likely to be struck by lightning while winning the lottery on the same day.
UUID v4 values generated with a CSPRNG (like this tool uses) are cryptographically random and suitable for session tokens. However, for API authentication, consider using longer tokens (256-bit) or established standards like JWT for additional features like expiration and claims.
They’re the same thing. UUID is the standard term used in RFC 4122 and most programming languages. GUID (Globally Unique Identifier) is Microsoft’s term, used in .NET, SQL Server, and Windows APIs. The format and generation methods are identical.
Use the count slider to generate up to 50 UUIDs per click. For larger batches, generate multiple times and combine the results. All generation happens instantly in your browser.
Yes. UUIDs contain only hexadecimal characters and hyphens, which are URL-safe. Many web applications use UUID-based URLs like /users/f47ac10b-58cc-4372-a567-0e02b2c3d479 to prevent ID enumeration attacks.
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