UUID generator

Example

Version: 4 · Count: 1

xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
y ∈ {8, 9, a, b}

This is a format diagram. Actual generated values change each time.

Technical details & limits

UUIDs contain 128 bits in 8-4-4-4-12 hexadecimal groups. v4 has 122 random bits after version and variant bits. This v7 implementation uses a 48-bit Unix millisecond timestamp plus random fields from crypto.getRandomValues. It has no monotonic counter within one millisecond.

About this tool

Generate batches of UUID v4 or v7, choose the quantity and letter case, and copy the results. v4 provides random identifiers; v7 carries a millisecond timestamp for approximate chronological ordering.

Use cases

• Seed a database with random primary keys.
• Produce message or session IDs for distributed systems.
• Pick v7 for records that must sort by creation time so B-tree indexes do not fragment.

How to use

1. Choose version (v4 or v7), count, and case.
2. Click Generate to produce one UUID per line, then copy the results.

Notes

v4 uses cryptographic randomness. This v7 implementation combines milliseconds with random fields and does not guarantee strict ordering within a millisecond.

FAQ

What is the difference between generated UUID v4 and UUID v7 values?

UUID v4 primarily uses random data, while v7 places a millisecond timestamp near the beginning. Both contain 128 bits; v4 has 122 random bits, and v7 uses a 48-bit timestamp. This implementation does not maintain a monotonic counter within a millisecond. Its v7 values can help group creation times, but their sorted order is not guaranteed to reproduce the generation order of values created together.

How many UUIDs can I generate in one batch?

This generator produces between 1 and 100 UUIDs per batch and offers versions v4 and v7. The standard text representation uses hexadecimal groups of 8-4-4-4-12 digits. Copy the completed batch after checking the selected version and count. The uppercase option changes only the textual presentation of hexadecimal letters, not the identifier's underlying bit value or the version and variant information encoded within it.

Are UUID v7 values generated in the same millisecond strictly ordered?

UUID v7 values generated within the same millisecond are not guaranteed to sort in generation order in this implementation. The first 48 bits contain the millisecond timestamp, while the complete identifier contains 128 bits with additional random fields. No monotonic counter resolves same-time ordering. If strict ordering is a business requirement, track a separate sequence or use an implementation that explicitly supplies the required monotonic behavior.

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