UUID Generator — Free Online UUID v1, v4 & v5 Generator
Generate cryptographically secure UUIDs instantly. Choose version, set quantity up to 100, customize format with uppercase, braces, or no-hyphens, and copy all in one click.
How to Use the UUID Generator
Generating UUIDs with ToolsInstant is instant and requires no registration. Follow these steps to get unique identifiers for any project.
Select UUID v4 for random IDs (most common), v1 for time-ordered IDs, v5 for deterministic name-based IDs, or v7 for sortable time-prefixed IDs.
Enter how many UUIDs you need (1–100). Toggle options like uppercase, remove hyphens, wrap in braces or quotes to match your system requirements.
Click Generate UUIDs. Copy individual entries or click "Copy All" to copy the entire list. Download as a .txt file for use in databases or code.
UUID Versions Explained
The RFC 4122 standard defines several UUID versions, each generated differently and suited for specific use cases. Understanding the differences helps you choose the right one.
Generated from the current timestamp (60-bit) and the MAC address of the generating machine. UUIDs are time-sortable and embed creation time information.
122 bits of cryptographically secure randomness. No embedded information — each UUID is completely random. The most widely used UUID version globally.
Deterministically generated from a namespace UUID and a name string using SHA-1. The same namespace + name always produces the same UUID, making it reproducible.
A newer format (RFC 9562) combining a millisecond-precision Unix timestamp with random bits. Naturally sortable like v1 but without embedded MAC addresses — better for privacy.
Common UUID Format Variations
Different systems and programming languages expect UUIDs in different formats. Our generator supports all major variations with a single click.
Why Use UUIDs?
UUIDs solve one of the most fundamental problems in distributed computing — generating unique identifiers without central coordination.
With 2¹²² possible values, UUID v4 collisions are statistically impossible. You can generate billions of UUIDs per second across millions of machines without conflicts.
Unlike auto-increment integers, UUIDs require no database sequence or coordination between servers. Perfect for microservices, mobile apps, and offline-first systems.
UUID v4 IDs are unpredictable and cannot be guessed or enumerated. They prevent ID-based data scraping and unauthorized resource access.
When merging databases or migrating data between systems, UUID primary keys eliminate ID conflicts — a critical advantage over sequential integers.
Supported by every major programming language, database, and framework. PostgreSQL, MySQL, MongoDB, Python, Go, Java, JavaScript — all have native UUID support.
The hyphenated format makes UUIDs easy to identify in logs, share verbally, and manually spot-check in database records and API responses.
Frequently Asked Questions
What is a UUID and what does it stand for?
UUID stands for Universally Unique Identifier. It is a 128-bit label used to uniquely identify objects in computer systems. Standardized as RFC 4122 (and updated in RFC 9562), UUIDs appear in the canonical form: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx — 32 hexadecimal digits in five groups separated by hyphens. The format is also known as GUID (Globally Unique Identifier), especially in Microsoft ecosystems.
What is the difference between UUID v4 and v1?
UUID v4 is randomly generated using a cryptographically secure random number generator (CSPRNG). It contains no embedded information and is the most privacy-friendly version. UUID v1 is generated from the current system clock timestamp and the machine's MAC address. v1 UUIDs are time-sortable but embed hardware information that could be a privacy concern. For most modern applications, v4 is recommended.
Are UUID v4 values truly unique?
Statistically, yes. UUID v4 uses 122 bits of randomness, giving 2¹²² ≈ 5.3 × 10³⁶ possible values. The probability of generating two identical UUIDs is astronomically small. To put it in perspective: if you generated 1 billion UUIDs per second for 100 years, the probability of a single collision would still be less than 1 in 10²⁵. For all practical purposes, they are guaranteed unique.
What is UUID v5 and when should I use it?
UUID v5 is a deterministic, name-based UUID generated using SHA-1 hashing. You provide a namespace UUID (like the DNS or URL namespace) and a name string. The same namespace + name combination always produces the exact same UUID. This is useful when you need stable, reproducible identifiers — for example, generating a consistent UUID for a specific domain name, product ID, or content hash across different systems without storing mappings.
What is UUID v7 and how is it different from v1?
UUID v7 (defined in RFC 9562) is a newer format that combines a Unix millisecond timestamp in the most significant bits with random data in the remaining bits. Like v1, it is time-sortable, making it excellent for database primary keys with B-tree indexes. Unlike v1, it does not embed MAC addresses, addressing the privacy concerns of v1. UUID v7 has become the recommended version for new systems requiring sortable unique IDs.
Can I use a UUID as a database primary key?
Yes, and it is a very common pattern. UUIDs as primary keys allow distributed systems to generate IDs without a central database sequence, simplify database merging and replication, and prevent ID enumeration attacks. The main trade-off is storage size (16 bytes vs 4-8 bytes for integers) and index performance with random UUIDs. UUID v7 or ULID-style ordered UUIDs are recommended for high-performance indexed columns as they insert in sorted order, reducing B-tree fragmentation.
What is the difference between UUID and GUID?
UUID and GUID refer to the same concept — a 128-bit unique identifier. UUID (Universally Unique Identifier) is the open standard term from the IETF RFC 4122. GUID (Globally Unique Identifier) is Microsoft's implementation of the same standard, used in Windows, .NET, COM, and SQL Server. They are fully compatible; a GUID is a UUID and vice versa. The formatting conventions are identical.
Are the UUIDs generated here safe and private?
Yes. All UUIDs are generated entirely within your browser using the Web Cryptography API (crypto.getRandomValues()). No data is sent to our servers, no UUIDs are logged or stored, and there is no network request involved in generation. The generated UUIDs are as private and secure as your browser's cryptographic random number generator allows.
What is the nil UUID?
The nil UUID is the special-case UUID with all 128 bits set to zero: 00000000-0000-0000-0000-000000000000. It is defined in RFC 4122 and used as a placeholder or null value in systems that require a UUID type but want to represent an empty or unset identifier. It is the UUID equivalent of NULL or 0 in other contexts.
How do I store UUIDs efficiently in a database?
Storage options vary by database: PostgreSQL has a native UUID type (16 bytes). MySQL/MariaDB can use BINARY(16) for efficiency or CHAR(36) for readability. SQL Server uses the UNIQUEIDENTIFIER type. MongoDB uses BSON's UUID subtype. Storing UUIDs as BINARY(16) rather than text saves significant space — about 20 bytes per row versus 36 bytes as a string, which adds up to gigabytes of savings in large tables.
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