Free Online UUID Generator
Generate v4 UUIDs with batch support and format options
701b8102-42f8-49f5-86d0-3515006be437Try these next
Why use UUID Generator
- Batch generation up to 100 UUIDs saves time when seeding databases or building test fixtures.
- Uses the Web Crypto API (crypto.getRandomValues), not Math.random(), so the output is production-grade.
- One-click copy for individual UUIDs or the entire batch.
- Uppercase/lowercase toggle and hyphen on/off match whatever format your system expects.
How it works
Each UUID v4 is a 128-bit value expressed as 32 hexadecimal digits in a 8-4-4-4-12 grouping separated by hyphens. The tool calls crypto.getRandomValues() to fill a 16-byte typed array with cryptographically secure random data. It then sets the version bits: the four most significant bits of byte 6 are set to 0100 (version 4), and the two most significant bits of byte 8 are set to 10 (RFC 4122 variant). The bytes are converted to hexadecimal strings and concatenated with hyphens at the correct positions. Because the Web Crypto API sources entropy from the operating system's CSPRNG, the output is unpredictable and suitable for use as database primary keys, idempotency tokens, or correlation IDs in distributed systems. Batch generation simply repeats this process N times.
About this tool
Most production databases need non-sequential primary keys. UUIDs are the standard answer -- 128-bit identifiers that are practically impossible to collide (odds are roughly 1 in 5.3 x 10^36). Generate one or batch-generate up to 100, toggle between uppercase and lowercase, and turn hyphens on or off for systems that store UUIDs as 32-character hex strings. Version 4 UUIDs are purely random and reveal nothing about when or where they were created, unlike v1 UUIDs which embed a timestamp and MAC address. The randomness here comes from the Web Crypto API (crypto.getRandomValues), not Math.random(), so the output is suitable for production use as database keys, idempotency tokens, or correlation IDs in distributed tracing.
How to use UUID Generator
- Set the quantity. Enter how many UUIDs you need -- 1 for a quick test, up to 100 for a seed file.
- Set the format. Toggle uppercase/lowercase and hyphens on/off to match what your system expects.
- Generate and copy. Hit Generate, then copy individual UUIDs or the whole batch in one click.
Use cases
- You're seeding a PostgreSQL test database and need 50 unique primary keys. Generate the batch, paste them into your INSERT script.
- Your offline-first mobile app needs to assign IDs to records before connectivity returns. Generate UUIDs client-side so they merge cleanly when the device syncs.
- Each test case in your API fixture file needs a unique resource ID. Generate 20 UUIDs, paste them into the JSON.
- A payment integration test requires an idempotency key per transaction. Generate a fresh UUID for each test run to prevent duplicate processing.
- Your microservice logging requires correlation IDs to trace requests across services. Grab a UUID for each test request.
Frequently Asked Questions
A UUID (Universally Unique Identifier) is a 128-bit number used to uniquely identify resources in computer systems. It is formatted as 32 hexadecimal characters separated by hyphens (e.g., 550e8400-e29b-41d4-a716-446655440000). UUIDs are also known as GUIDs (Globally Unique Identifiers) in Microsoft ecosystems.
UUID v1 is generated using a timestamp and the machine's MAC address, which means it can reveal information about when and where it was created. UUID v4 is generated using random or pseudo-random numbers, making it the preferred choice for most applications because it does not leak any identifying information.
While theoretically possible, the probability of generating two identical UUID v4 values is astronomically low -approximately 1 in 5.3 × 10^36. You would need to generate about 2.71 quintillion UUIDs to have a 50% chance of a single collision, making duplicates effectively impossible in practice.
UUID v4 values generated with a cryptographically secure random number generator (like the Web Crypto API used by this tool) have strong randomness. However, UUIDs are not designed as security tokens. For authentication tokens or API keys, use a dedicated secret generator with higher entropy and proper encoding.
A UUID follows the format xxxxxxxx-xxxx-Mxxx-Nxxx-xxxxxxxxxxxx, where each x is a hexadecimal digit (0–9, a–f). The M digit indicates the UUID version (4 for random), and the N digit indicates the variant (8, 9, a, or b for RFC 4122). The total length is 36 characters including hyphens.
This tool lets you generate up to 100 UUIDs in a single batch. Simply set the quantity you need and click generate. All UUIDs are created instantly in your browser and can be copied to your clipboard with one click.
UUIDs can be generated independently on any machine without coordination, making them ideal for distributed systems, microservices, and offline-first applications. They also prevent information leakage -unlike sequential IDs, UUIDs do not reveal how many records exist or the order in which they were created.
UUIDs are widely used as primary keys in databases, identifiers for API resources, session tokens, correlation IDs in distributed tracing, file names for uploaded content, and transaction identifiers in payment systems. They are supported natively by most programming languages and databases including PostgreSQL, MySQL, and MongoDB.
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