UUID Generator
Generate unique identifiers (UUID, ULID, NanoID)
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About This Tool
Generate universally unique identifiers (UUIDs), ULIDs, and NanoIDs instantly with our comprehensive online tool. Our UUID Generator supports multiple UUID versions including v1 (timestamp-based), v4 (random), and v7 (modern timestamp-random hybrid), making it the most versatile UUID generator available. Whether you need database primary keys, distributed system identifiers, API tokens, or session IDs, our tool provides cryptographically secure identifiers that follow RFC 4122 standards. Generate single IDs or bulk create up to 1000 identifiers at once, with format options for different use cases. Perfect for developers, database administrators, system architects, and anyone building applications that require unique identification.
What is a UUID?
A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit identifier standardized by RFC 4122. UUIDs are designed to be unique across space and time without requiring a central registration authority. The standard UUID format is 32 hexadecimal digits displayed in five groups separated by hyphens: 8-4-4-4-12 (for example: 550e8400-e29b-41d4-a716-446655440000). With 2^122 possible unique values, the probability of generating duplicate UUIDs is astronomically small - you could generate 1 billion UUIDs every second for 100 years and still have only a 50% probability of creating one duplicate. This makes UUIDs ideal for distributed systems where coordination between generators is impractical.
How to Use This UUID Generator
Using our UUID Generator is simple: select your desired identifier type (UUID v1, v4, v7, ULID, or NanoID), specify how many you need (1-1000), and click Generate. The generated identifiers appear in the output area, ready to copy. Use the format options to customize output for different use cases - uppercase for constants, braces for .NET/Windows applications, or no hyphens for compact storage. The bulk generation feature is perfect for seeding databases or creating test data. For validation and analysis, use the Decode tab to paste any UUID and see its version, variant, and extracted timestamp (for v1/v7). All generation happens in your browser using cryptographically secure random number generators, ensuring both privacy and quality. The Copy button copies all generated IDs to your clipboard, while Download exports them as a text file.
Frequently Asked Questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122 that is unique across space and time. Also known as GUID (Globally Unique Identifier), UUIDs are represented as 32 hexadecimal characters in the format 8-4-4-4-12, for example: 550e8400-e29b-41d4-a716-446655440000. With approximately 5.3 undecillion possible values, UUIDs are designed to be generated independently without coordination while maintaining practical uniqueness.
What is the difference between UUID and GUID?
UUID and GUID are the same thing - both refer to 128-bit unique identifiers following the RFC 4122 standard. The term GUID (Globally Unique Identifier) is primarily used in Microsoft technologies and Windows environments, while UUID (Universally Unique Identifier) is used everywhere else. They have identical structure and serve the same purpose. The format and generation algorithms are completely interchangeable.
Which UUID version should I use?
For most applications, use UUID v4 (random) as it's the most common and provides excellent uniqueness without exposing system information. Use UUID v7 (or ULID) when you need database-friendly sortable IDs that improve index performance and maintain chronological ordering. Avoid UUID v1 in modern applications as it exposes MAC addresses and offers no advantages over v7. For the shortest URL-safe identifiers, consider NanoID. For maximum compatibility across systems and languages, stick with standard v4 UUIDs.
Can UUIDs collide or duplicate?
The probability of UUID collision is so astronomically small it's effectively zero for practical purposes. With 2^122 possible values for v4 UUIDs, you would need to generate 1 billion UUIDs per second for 100 years to have just a 50% chance of one collision. You're more likely to experience hardware failure or data corruption than a true UUID collision. For comparison, it's equivalent to winning the lottery multiple times in a row. In distributed systems with proper random number generation, UUID collisions are not a realistic concern.
What is the difference between UUID and ULID?
While both are 128-bit unique identifiers, ULIDs (Universally Unique Lexicographically Sortable Identifiers) offer specific advantages: ULIDs are sortable by creation time, use base32 encoding (26 characters vs UUID's 36 with hyphens), are URL-safe without encoding, and are case-insensitive. UUIDs are the established standard with universal support, while ULIDs are newer and offer better readability and database performance. Choose UUIDs for maximum compatibility, ULIDs when sortability and compactness matter. Both provide equivalent uniqueness guarantees.
Are UUIDs secure for authentication tokens?
UUID v4 (random) provides adequate entropy for many authentication use cases with 122 bits of randomness, making them resistant to guessing attacks. However, for high-security applications, consider tokens with 256+ bits of entropy. Never use UUID v1 for security tokens as they expose timestamp and MAC address information. UUID v7 can be used for tokens but reveals approximate creation time. For session IDs and API keys, v4 UUIDs are commonly used and considered secure when generated with cryptographically secure random number generators (CSPRNG), which this tool uses.
How do I extract timestamp from a UUID?
Only UUID v1 and v7 contain timestamps. For v1 UUIDs, the timestamp is encoded in the first three groups using a 60-bit value representing 100-nanosecond intervals since October 15, 1582 (Gregorian calendar). For v7 UUIDs, the timestamp is in the first 48 bits as Unix epoch milliseconds. Our UUID Decoder tool can automatically extract and display timestamps from v1 and v7 UUIDs. UUID v4 (random) contains no timestamp information and cannot be decoded for time data.
Are UUIDs case-sensitive?
Technically, UUIDs are case-insensitive according to RFC 4122 - both uppercase and lowercase hexadecimal representations are valid and equivalent. However, the standard recommends using lowercase for output. Most databases and programming languages treat UUIDs case-insensitively, so '550E8400-E29B-41D4-A716-446655440000' and '550e8400-e29b-41d4-a716-446655440000' are considered identical. For consistency and compatibility, it's best practice to use lowercase unless your specific use case requires uppercase.
What is a Nil UUID?
A Nil UUID (also called empty or null UUID) is a special UUID where all 128 bits are set to zero: 00000000-0000-0000-0000-000000000000. It's defined in RFC 4122 to represent a null or non-existent UUID value, similar to how null represents absence of a value in programming. Nil UUIDs are useful as placeholder values, default values in configurations, or to indicate 'no UUID assigned' situations. They should never be used as actual identifiers since they're not unique.
Can I use UUIDs as database primary keys?
Yes, UUIDs make excellent database primary keys, especially in distributed systems. They allow independent record creation without coordination, prevent ID conflicts when merging databases, and avoid sequential ID enumeration attacks. However, choose wisely: random v4 UUIDs can cause index fragmentation in some databases due to their random nature. For better database performance, use UUID v7 or ULID which are timestamp-ordered and naturally clustered, improving index efficiency and query performance. Most modern databases have native UUID support with optimized storage (16 bytes instead of 36-character strings).