UUID Generator
Instantly generate one or hundreds of UUIDs and ULIDs. Choose version, format, and copy with one click.
Version
Format
UUID v4 uses crypto.randomUUID() — cryptographically secure
How to use UUID Generator
The UUID Generator creates universally unique identifiers (UUIDs) in bulk, supporting UUID v1 (time-based), v4 (random) and v5 (namespace + name SHA-1 hash). UUIDs are 128-bit identifiers formatted as 32 hexadecimal digits grouped by hyphens (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx). They are used as database primary keys, distributed transaction IDs, file names and session tokens that must be globally unique without central coordination.
- Select the UUID version: v4 for a random UUID, v1 for a time-based UUID, or v5 for a deterministic namespace-hash UUID.
- For v5, enter the namespace (DNS, URL, OID or X.500) and the name string.
- Set the quantity — generate 1 to 1,000 UUIDs at once.
- Choose the output format: hyphenated (standard), compact (no hyphens), uppercase or lowercase.
- Click Generate and copy the results or download them as a plain-text file.
Your data never leaves your device — 100% private processing.
UUID versions and when to use each
UUID v4 is the most popular choice: 122 of its 128 bits are randomly generated, giving a collision probability so low it is negligible for all practical purposes. UUID v1 embeds a 60-bit timestamp and a 48-bit node identifier (MAC address), making it sortable by creation time but leaking machine identity. UUID v5 is deterministic — the same namespace and name always produce the same UUID, making it useful for generating stable identifiers for well-known resources (e.g., a UUID for a given URL).
| Version | Generation method | Sortable | Deterministic | Best use case |
|---|---|---|---|---|
| v1 | Timestamp + MAC address | Yes (time) | No | Distributed systems needing time ordering |
| v4 | Random (122 bits) | No | No | Database primary keys, session tokens |
| v5 | SHA-1 of namespace + name | No | Yes | Stable IDs for named resources |
UUIDs as database primary keys
Using UUIDs as primary keys enables records to be created on the client or in microservices without consulting a central sequence generator, preventing the bottleneck of auto-increment IDs in distributed architectures. The trade-off is index fragmentation in B-tree databases (PostgreSQL, MySQL) because random UUIDs insert at arbitrary positions in the index. UUID v7 (RFC 9562, 2024) addresses this with a time-ordered random UUID that combines the monotonicity of v1 with the privacy of v4.
Glossary
- UUID
- Universally Unique Identifier — a 128-bit label standardised by RFC 4122 that is unique across space and time.
- GUID
- Globally Unique Identifier — Microsoft's name for UUID, using the same format and standard.
- Namespace
- In UUID v5, a predefined UUID (e.g., DNS or URL) that scopes the generated ID to a particular domain.
- Entropy
- Randomness gathered from hardware or OS sources to ensure UUIDs are unpredictable and non-repeating.
- RFC 4122
- The IETF standard defining UUID structure, variants, and versions 1 through 5.
Related reading
Frequently Asked Questions
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Why use UUID Generator?
- No installation — use directly from any browser
- Handles large inputs without crashing or timeouts
- Syntax highlighting and formatted output for readability
- Copy to clipboard shortcut for fast workflow integration
Common use cases
- Validate and format JSON responses from APIs
- Encode/decode Base64 strings during debugging
- Generate UUIDs for database seeds or test data
- Minify CSS or JavaScript before deployment
- Diff two code snippets to spot regressions
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