Overview
Generate UUID v4 identifiers in bulk
A UUID (Universally Unique Identifier) is a 128-bit value used to identify something with extremely low risk of collision, even without a central authority. UUID version 4 specifically is built from random data, which makes it the most popular flavor in modern software. Database primary keys, session tokens, file names, idempotency keys, distributed system message IDs, and test fixtures all rely on UUIDs.
ToolHub UUID Generator creates up to 500 UUIDs at once using your browser cryptographically secure random source. You can format the output four different ways and copy any single UUID or the entire batch with a click.
Step-by-step
How to generate UUIDs
- 1
Pick how many you need
Use the slider to choose between 1 and 500 UUIDs. The output updates instantly as you change the count. - 2
Choose a format
Standard is the canonical hyphenated form. No hyphens removes the dashes for use in URLs and file names. Uppercase converts letters to capitals (still hyphenated). Braces wraps each UUID in curly braces, the format used in some Microsoft tooling. - 3
Copy or download
Click any UUID to copy it individually, copy all to grab the full list as newline-separated text, or download a .txt file for use in your tooling.
Background
UUID v4 explained
A canonical UUID looks like 550e8400-e29b-41d4-a716-446655440000. The 32 hex digits represent 128 bits of data, written as 5 groups separated by hyphens. UUID version 4 reserves a few bits to identify itself as version 4 (the 13th hex digit is always 4) and 2 bits for variant, leaving 122 bits of randomness.
With 122 bits of randomness, the chance of collision is astronomically small. You would need to generate one billion UUIDs every second for about 85 years before the chance of a single collision reaches 50 percent. For practical purposes, UUID v4 values are unique.
Versions you might encounter
- v1: time-based, includes a timestamp and MAC address. Predictable, leaks identity.
- v3 / v5: hash-based. Same input produces same UUID. Useful for deterministic IDs.
- v4: random. Most common. What this tool generates.
- v6 / v7: newer time-ordered variants. Better for database indexing but less universal.
Use cases
When to use UUIDs
Database primary keys
Use UUIDs instead of auto-increment IDs to avoid conflicts when merging data from multiple sources.
Session and request tokens
Generate unique identifiers per user session, request, or transaction for logging and tracing.
File and folder names
Avoid name collisions in user uploads by storing files with UUID names and the original name as metadata.
Idempotency keys
Send a UUID with each API request so retries do not create duplicate records.
Test data
Seed development databases with realistic-looking unique IDs.
Distributed message IDs
Use UUIDs to track messages across queues, microservices, or event streams.
Common questions
Are these cryptographically secure?
Yes. The generator uses crypto.randomUUID, the browser standard API backed by your operating system cryptographic random number generator. The same source is used for HTTPS keys.
Can I use these in production?
Absolutely. They follow RFC 4122 v4 exactly. Every major language and database (PostgreSQL, MySQL, MongoDB, .NET, Java, Python, Node) accepts them.
Why use UUIDs instead of auto-increment IDs?
Auto-increment IDs leak information (a competitor can estimate your user count from the highest ID), break when merging data from multiple databases, and require a round trip to the database to reserve. UUIDs can be generated client-side and are unique by design.
What is the format with no hyphens for?
Useful for URL slugs, file names, and any context where hyphens may interfere with parsing. The data is identical, just the visual representation changes.
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