UUID & ULID Generator — Bulk & Secure
Generate UUIDs (v4) and ULIDs in bulk. Cryptographically secure, browser-based. Generate up to 50 IDs at once. Free online tool.
What are UUIDs and ULIDs?
A UUID (Universally Unique Identifier) is a 128-bit value used to uniquely identify records in databases, API requests, and distributed systems. Version 4 UUIDs are randomly generated using cryptographic randomness, making collisions practically impossible.
A ULID (Universally Unique Lexicographically Sortable Identifier) combines a 48-bit timestamp with 80 bits of randomness. Unlike UUIDs, ULIDs are sortable by creation time, making them ideal for database primary keys where insertion order matters.
Both formats are generated entirely in your browser using the Web Crypto API. No data is sent to any server. Generate up to 50 identifiers at once, toggle between formats, and copy results with a single click.
How the UUID Generator Works
- Click Generate to create a new UUID v4
- The UUID is generated using cryptographically secure randomness
- Generate multiple UUIDs at once if needed
- Copy any UUID to your clipboard with one click
When to Use UUIDs
UUIDs (Universally Unique Identifiers) are 128-bit identifiers that are virtually guaranteed to be unique across all systems without coordination. UUID v4 uses random generation and is the most commonly used version. They are ideal for database primary keys in distributed systems, API resource identifiers, and session tokens. The probability of a collision is astronomically low — about 1 in 5.3 billion billion.
When to Use a UUID Generator
Use UUIDs as database primary keys in distributed systems where auto-incrementing integers would collide, as API resource identifiers that don't reveal record counts, as session tokens and correlation IDs for request tracing, and as unique filenames for uploaded content. Use ULIDs when you need the sortability benefit of timestamps combined with uniqueness.
Common Use Cases
- •Generate database primary keys for distributed systems where auto-increment would collide Hash Generator — SHA-256, SHA-512 & More
- •Create unique API resource identifiers that don't reveal record counts or creation order
- •Generate correlation IDs for request tracing across microservices
- •Create unique filenames for uploaded content to prevent collisions and overwrites
- •Generate test data identifiers for development and QA environments Strong Password Generator — Secure & Random
Expert Tips
- ✱Use ULID instead of UUID when you need chronological sorting — the timestamp prefix enables ORDER BY without a separate created_at column
- ✱In PostgreSQL, use gen_random_uuid() for server-side UUID generation rather than generating in application code — it is faster and ensures consistency
- ✱When using UUIDs as URL parameters, consider lowercase format without hyphens for shorter, cleaner URLs
Frequently Asked Questions
- UUID v4 is purely random (122 bits of randomness) and not sortable. ULID combines a 48-bit millisecond timestamp with 80 bits of randomness, making it chronologically sortable. ULIDs are ideal for database primary keys where insertion order matters.
- Theoretically yes, but practically no. UUID v4 has 2^122 possible values. You would need to generate about 2.7 quintillion UUIDs to have a 50% chance of a single collision. For all practical purposes, UUID collisions do not happen.
- UUIDs prevent ID enumeration attacks and work well in distributed systems. However, random UUIDs can fragment B-tree indexes. Consider ULIDs or UUID v7 (timestamp-ordered) for better database performance. For single-server applications, auto-incrementing integers are simpler.
- Yes. UUIDs and ULIDs are generated using the Web Crypto API (crypto.getRandomValues), which provides cryptographically secure randomness. No data leaves your browser.
What is the difference between UUID and ULID?▾
Can UUIDs collide?▾
Should I use UUIDs as database primary keys?▾
Is this generator secure?▾
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