SuperDevTools
EN

UUID Generator (v4 and v7)

Version

Tip: press the space bar for a new batch.

Validate or decode a UUID

Paste a UUID to see its version, its variant and, for a v7, the time it was created.

UUIDs are created in your browser by its cryptographic random generator. Nothing is sent or stored.

Generate v4 or v7 UUIDs in your browser

A UUID (universally unique identifier) is a 128-bit number written as 32 hexadecimal digits in five groups of 8, 4, 4, 4 and 12 characters: 550e8400-e29b-41d4-a716-446655440000. It labels a database row, a file or an order without asking a central server for the next number. A GUID (globally unique identifier), the name you meet in C# and on desktop platforms, is exactly the same thing, so this page works as a GUID generator too.

Every identifier comes from your browser's cryptographic random generator. Nothing is sent to our server and nothing is stored.

How to use it

  1. Pick the version: "UUID v4 (random)" or "UUID v7 (time-ordered)".
  2. Set "How many UUIDs (1 to 1000)" and click "Generate". The space bar gives you a fresh batch.
  3. Adjust the layout with "Uppercase", "No hyphens", "Wrap in braces { }", "Wrap in quotes" and "Comma at end of line". Tick the last two and the list drops straight into a JSON array, a Python list or a SQL IN (...) clause.
  4. Grab the result with "Copy all" or "Download (.txt)", one UUID per line.

The "Validate or decode a UUID" box accepts an identifier with or without hyphens, in capitals, inside braces or prefixed with urn:uuid:. It shows the version, the variant and, for a v7, the embedded timestamp. Anything that is not exactly 32 hex digits is rejected.

Version 4 or version 7?

In a UUID v4, 122 of the 128 bits are random. The remaining 6 bits mark the version (the digit 4 in position 13) and the variant (8, 9, a or b in position 17). It gives nothing away, neither the time nor the machine, which makes it the right pick for tokens, file names and IDs that appear in a URL.

A UUID v7, standardised in 2024 by RFC 9562, starts with the Unix time in milliseconds on 48 bits, followed by 74 random bits. As a result, v7 values sort in creation order, even as plain strings. For a database primary key that matters: new rows land at the end of the index instead of at random places, so you get less page splitting and fewer writes. When the tool creates several v7 values in the same millisecond, it adds a random step to the random part, so the list is always strictly increasing. The trade-off: a v7 reveals when it was made.

Version 1 is not offered, because it embeds the machine's network address alongside the time and RFC 9562 now recommends version 7 instead.

Decoding example: paste 017f22e2-79b0-7cc3-98c4-dc0c0c07398f. The first twelve digits, 017f22e279b0, equal 1,645,557,742,000 milliseconds, which is 22 February 2022 at 19:22:22.000 UTC, or 2:22:22 pm in New York.

Can two UUIDs ever clash?

In theory yes, in practice no. A v4 has 2 to the power of 122 possible values, about 5.3 undecillion (a 37-digit number). Using the birthday calculation, you would need to create about 103 trillion v4 UUIDs to reach a one-in-a-billion chance of a single duplicate. With one billion UUIDs, the odds are roughly 9 in 100 quintillion. That assumes a good random source, which is what this page uses. For v7, only IDs created in the same millisecond can collide, and even then all 74 random bits would have to match.

Frequently asked questions

Is a GUID different from a UUID?

No. GUID is simply another name for the same 128-bit format. GUIDs are often shown in capitals inside braces, such as {3F2504E0-4F89-41D3-9A0C-0305E82C3301}, which is why the tool has "Uppercase" and "Wrap in braces { }".

Should I store a UUID as text or binary?

Use 16 bytes of binary when your database allows it (a native uuid type or BINARY(16)). That is less than half the size of the 36-character string. Keep the hyphenated form for display and APIs.

Can a UUID be used as a secret link?

A v4 from a cryptographic generator, like the ones here, is unpredictable enough for a share link. A v7 is not: its first 48 bits give away the exact creation time, which shrinks the part an attacker has to guess.