UUID Generator — Generate UUID v4 Online
Generate cryptographically random UUID v4 identifiers instantly. Generate one at a time or bulk-generate up to 100 UUIDs for testing and development.
How to Generate UUIDs
- 1Click 'Generate UUID' for a single UUID
- 2Set the count (up to 100) and click 'Generate Bulk' for multiple UUIDs
- 3Toggle uppercase or no-dashes format as needed
- 4Click any UUID to copy it, or use 'Copy All' for bulk
Key Benefits
- Cryptographically secure random generation
- Bulk generate up to 100 UUIDs at once
- Format options: uppercase, no-dashes
- Click any result to copy it instantly
Frequently Asked Questions
What is a UUID?
A UUID (Universally Unique Identifier) is a 128-bit identifier standardized in RFC 4122, written as 32 hexadecimal digits in five groups separated by hyphens (8-4-4-4-12). They are designed to be globally unique without requiring a central registry or coordination between systems. UUID v4 uses random numbers for 122 of those bits, making the chance of two machines independently generating the same UUID vanishingly small.
Are these UUIDs truly random?
Yes. This tool uses the browser's built-in crypto.randomUUID(), which draws from a cryptographically secure random number generator. This is the same source used for cryptographic operations, so the randomness is of high quality — not a predictable pseudo-random sequence.
What is the format of a UUID v4?
A UUID v4 looks like: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx. The 4 in position 13 identifies the version (v4). The y in position 17 is always 8, 9, a, or b — this identifies the variant (RFC 4122). All other characters are random hex digits. The format option to remove dashes outputs the same 32 hex characters as a compact string.
How likely is it to generate two identical UUIDs?
UUID v4 has 122 bits of randomness. To have a 50% chance of any collision you would need to generate approximately 2.7 quintillion UUIDs (2.7 × 10^18). At a rate of 1 billion UUIDs per second, that would take about 85 years. For any realistic use — including large-scale databases and distributed systems — UUIDs are safe to treat as globally unique without checking for duplicates.
When should I use a UUID instead of a sequential integer ID?
Use UUIDs when IDs must be generated independently on multiple servers without coordination, when you want to avoid revealing record counts (a sequential ID of 10001 signals you have at least 10,000 records), or when merging data from different sources. Use sequential integers when raw database performance is the priority — integers index and join faster in most relational databases, and they are easier to read and debug.
What is the difference between UUID v4 and other UUID versions?
UUID v1 encodes the current timestamp and the machine's MAC address, making it time-sortable but leaking machine information. UUID v3 and v5 are deterministic: they hash a name within a namespace (v3 uses MD5, v5 uses SHA-1), producing the same UUID for the same input every time — useful for consistent identifiers for known entities. UUID v4 is purely random with no embedded information, which is why it is the most common choice for general-purpose unique IDs.