What is the difference between UUID v4 and v7?

UUID v4 is fully random. UUID v7 embeds a Unix timestamp in the first 48 bits, making it time-sortable. v7 is better for database primary keys because it maintains insertion order in B-tree indexes.

Can two UUIDs ever be the same?

Theoretically yes, but the probability is astronomically low. A UUID v4 has 122 random bits, giving about 5.3 x 10^36 possible values. You would need to generate about 2.7 x 10^18 UUIDs to have a 50% chance of a single collision.

Is it safe to generate UUIDs in the browser?

Yes. Modern browsers use crypto.getRandomValues() which provides cryptographically strong random numbers. DevToolHQ uses this API, so the UUIDs are just as random as those generated server-side.

Last updated: April 12, 2026

Best UUID Generator Online in 2026

Quick Answer

DevToolHQ UUID Generator is the best pick: it generates UUIDs instantly in the browser with support for v1, v4, and v7. No data is sent to any server, and you can generate in bulk.

Rankings

#	Tool	Why
#1	DevToolHQ UUID Generator	Generates v1, v4, and v7 UUIDs entirely client-side with bulk generation and one-click copy.
#2	UUIDGenerator.net	Well-established site with support for multiple UUID versions and a clean interface.
#3	Online UUID Generator	Good reference site with UUID decoding, validation, and timestamp extraction.

Detailed Breakdown

DevToolHQ UUID Generator

Generates v1, v4, and v7 UUIDs entirely client-side with bulk generation and one-click copy.

Pros

+Client-side generation — cryptographically random
+Supports UUID v1, v4, and v7
+Bulk generation up to 1000 at once

Cons

-No UUID v5 (namespace-based) generation yet

UUIDGenerator.net

Well-established site with support for multiple UUID versions and a clean interface.

Pros

+Supports v1, v3, v4, v5 generation
+Nil UUID and GUID options
+Educational content about UUID versions

Cons

-Contains ads
-Server-side generation for some versions

Online UUID Generator

Good reference site with UUID decoding, validation, and timestamp extraction.

Pros

+UUID decoder and validator
+Timestamp extraction from v1 UUIDs
+Clean interface

Cons

-Ad-supported
-Fewer generation options than UUIDGenerator.net

Tips

1.Use UUID v4 for most applications — it is random and has negligible collision probability.
2.Use UUID v7 for database primary keys — it is time-sortable, which improves index performance.
3.Never use UUID v1 in public-facing IDs — it contains the MAC address of the generating machine.
4.For testing, use a fixed UUID rather than generating fresh ones to make tests deterministic.

Frequently Asked Questions

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