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Owais Khan Software Reviews

UUID Generator

Random, time-ordered and name-based UUIDs, generated on your device.

Generate UUIDs

5 version 4 UUIDs.

Decode a UUID

Version7 — Unix time-based, sortable
VariantRFC 9562 / RFC 4122
Created2022-02-22T19:22:22.000Z

UUID v7 generator for database keys

Random v4 keys scatter new rows across a database index, which slows inserts as tables grow. A UUID v7 begins with a millisecond timestamp, so keys created later sort later — the decoder above shows the timestamp inside the RFC’s own example, 017F22E2-79B0-7CC3-98C4-DC0C0C07398F, created on 22 February 2022. PostgreSQL 18 added a built-in uuidv7() for the same reason.

Bulk UUID generator

Need test data or seed rows? Set “How many” up to 10,000 and download the list as a text file, one UUID per line. v7 UUIDs in a batch are guaranteed to come out in increasing order, even when thousands are made in the same millisecond.

GUID generator

A GUID is the same 128-bit identifier under Microsoft’s name. For .NET, registry keys or Visual Studio, choose the UPPERCASE or {braces} format; this works as a GUID generator producing standard version 4 values, identical to Guid.NewGuid() output.

Frequently asked questions

What is a UUID?
A universally unique identifier: a 128-bit value written as 32 hexadecimal digits in five groups, like 919108f7-52d1-4320-9bac-f847db4148a8. It can be created anywhere, without a central registry, with a negligible chance of ever colliding with another. GUID is Microsoft’s name for the same thing. The format is defined by RFC 9562, which replaced RFC 4122 in 2024.
Which UUID version should I use?
Version 4 for identifiers that should reveal nothing — it is 122 random bits. Version 7 for database primary keys: it starts with the creation time in milliseconds, so new rows land at the end of the index instead of at random places, which keeps inserts fast. Version 5 when the same input must always give the same UUID, such as an ID derived from a URL or email address. Version 1 is legacy; prefer 7.
Are UUIDs really unique?
In practice, yes. A version 4 UUID has 122 random bits: you would need to generate about 2.7 quintillion of them to have a 50% chance of a single duplicate. This generator uses crypto.getRandomValues, the browser’s cryptographically secure source, not Math.random — which is what makes that estimate hold.
What is the difference between UUID v4 and UUID v7?
Both are 128 bits with the same text format. In v4 almost everything is random. In v7 the first 48 bits are a Unix timestamp in milliseconds, followed by random bits, so v7 UUIDs sort in the order they were created and reveal roughly when. Paste a v7 UUID into the decoder to see its time. Within one generated batch this tool also keeps v7 UUIDs strictly increasing.
How do name-based (v5 and v3) UUIDs work?
They hash a namespace UUID together with a name — SHA-1 for version 5, MD5 for version 3 — so the same namespace and name always produce the same UUID. The standard namespaces are DNS, URL, OID and X.500; for example, the DNS namespace and "www.example.com" always give 2ed6657d-e927-568b-95e1-2665a8aea6a2. Put one name per line to generate several.
Is it safe to generate UUIDs in the browser?
Yes. They are generated on your device with the browser’s cryptographic random number generator. Everything involved — the random bytes, the names you hash, the UUIDs themselves — never leaves your browser, so there is no server that could log them. That is enforced rather than promised: this site’s test suite scans the shipped HTML for every browser API capable of sending data off the page and fails the build if it finds one.