About This Tool
A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify information in computer systems. Because the probability of generating a duplicate is virtually zero, UUIDs are perfect for database keys, session IDs, and transaction references. Every modern software system, from mobile apps to distributed microservices, relies on unique identifiers to track records without collisions. Our Free UUID Generator creates Version 4 (random) UUIDs instantly. You can generate up to 1,000 at a time and customize the format to match your database requirements, including uppercase hex digits, optional hyphens, and curly braces for Microsoft GUID notation. Whether you need a single UUID for a quick test or a batch of hundreds for seeding a development database, this tool produces standards-compliant identifiers in one click. Results are available for immediate copy or download, and no signup or registration is required.
What is a UUID v4?
Version 4 UUIDs are generated using random numbers. A v4 UUID format looks like this: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The 4 in the third group indicates the version, and the first hex digit of the fourth group (the y position) is restricted to 8, 9, A, or B to indicate the "variant" field. This ensures that any v4 UUID you generate follows the standard RFC 4122 specification and can be distinguished from other UUID versions.
The standard format uses 32 hexadecimal digits separated by four hyphens into five groups (8-4-4-4-12). Some systems require the hyphens, while others strip them for compact storage. This generator lets you toggle hyphens on or off to match your target system.
UUID vs GUID
They are effectively the same thing. UUID stands for Universally Unique Identifier, while GUID (Globally Unique Identifier) is the term preferred by Microsoft. Both refer to the 128-bit identifier standard defined in RFC 4122.
Microsoft systems (SQL Server, .NET, PowerShell) typically display GUIDs with curly braces: {550e8400-e29b-41d4-a716-446655440000}. Most other platforms omit the braces. This generator includes a "Add Braces" option for Microsoft-compatible output. The underlying identifier is identical regardless of formatting.
Collision Probability
The total number of possible v4 UUIDs is 2^122 (approximately 5.3 x 10^36). To put this in perspective, you would need to generate 1 billion UUIDs per second for 85 years to have a 50% chance of a single collision. For all practical purposes, they are unique.
This astronomical number of possibilities means that even large-scale distributed systems generating millions of UUIDs per day across hundreds of servers have essentially zero risk of duplicates. The probability is so low that UUID collisions are not a realistic failure mode in any production system.
Common UUID Use Cases
UUIDs appear throughout modern software development:
- Database primary keys: UUIDs are ideal primary keys for distributed databases where auto-incrementing integers would cause conflicts across shards or replicas. PostgreSQL, MySQL, and MongoDB all support UUID columns natively.
- API request tracing: Assigning a UUID to each API request lets you trace it through logs across multiple services. This is essential for debugging microservice architectures.
- Session management: Web applications use UUIDs as session tokens because their randomness makes them impossible to guess, providing security against session hijacking.
- File and resource naming: Uploaded files, temporary resources, and cache keys often use UUIDs to avoid naming conflicts without requiring a centralized naming authority.
- Message queues: Systems like Kafka, RabbitMQ, and SQS use UUIDs to identify individual messages for deduplication and idempotent processing.
UUID Formatting Options Explained
This generator supports three formatting toggles that cover the most common requirements across different platforms and databases:
- Uppercase (A-F): By default, UUIDs use lowercase hex digits (a-f). Toggling uppercase produces A-F instead. Some systems normalize to uppercase, others to lowercase. PostgreSQL stores UUIDs in lowercase, while Microsoft SQL Server uses uppercase.
- Hyphens: The standard format includes four hyphens (36 characters total). Removing hyphens produces a compact 32-character string that saves storage space in databases and URLs. Both formats are valid and interchangeable.
- Braces: Wrapping the UUID in curly braces produces the GUID format used by Microsoft platforms:
{550e8400-e29b-41d4-a716-446655440000}. Enable this when generating identifiers for .NET applications, SQL Server, or Windows Registry entries.
You can combine all three options. For example, an uppercase UUID with no hyphens and braces would look like: {550E8400E29B41D4A716446655440000}.