UUID Generator

What you can do with this UUID tool

• Generate UUID v4 with crypto.randomUUID() when available
• Generate time-ordered UUID v7 with crypto.getRandomValues()
• Create one UUID or a batch of up to 500
• Uppercase or lowercase output
• Hyphenated 8-4-4-4-12 format or compact 32-character hex
• Copy one UUID, copy all, or download a text file
• Validate a pasted UUID and detect its version
• Private by design: values stay in your browser

What is a UUID?

A UUID (Universally Unique Identifier), also called a GUID in some Microsoft APIs, is a 128-bit value. The common text form is eight hex digits, a hyphen, four, four, four, then twelve — 36 characters including hyphens. UUIDs are designed so independent systems can mint identifiers without a central counter.

UUID v4 vs UUID v7

UUID v4 is the usual random UUID. The version nibble is 4, the variant bits follow RFC 4122 / RFC 9562, and the rest of the bits come from a secure random source. It is a good default for database keys, object IDs, and request IDs when you do not need sort order.

UUID v7 puts a 48-bit Unix millisecond timestamp in front, then fills the remaining bits with random data. Values generated close together tend to sort in creation order, which can help index locality. UUID v7 is not a secret: anyone who sees the value can recover the approximate creation time.

This page defaults to UUID v4. Choose v7 only when time-ordering is useful. Other versions (1, 3, 5, and so on) are not generated here; the validator can still detect them if you paste one.

How does this random UUID generator work?

For UUID v4, the tool prefers the native Web Crypto helper crypto.randomUUID(). If that function is missing, it fills 16 bytes with crypto.getRandomValues() and sets the version and variant bits. UUID v7 is implemented from RFC 9562 using the same secure random source plus the current Unix time. If secure randomness is unavailable, generation is refused rather than silently using Math.random().

How to use the online UUID generator

1. 1Select UUID v4 for a random ID or UUID v7 for a time-ordered ID.
2. 2Set the quantity (1–500) and choose uppercase or hyphenated output.
3. 3Click Generate, then copy, copy all, or download the list.
4. 4Optional: paste an existing UUID into the validator to confirm the format and version.

UUID validator

The validator checks whether a pasted string is a well-formed 128-bit UUID. It accepts the common hyphenated form, a 32-character hex string, optional urn:uuid: prefixes, and curly braces. It then reads the version nibble and variant bits so you can tell a v4 value from a v1 or v7 value. An invalid string is rejected with a short, actionable message — the page does not crash on bad input.

Limitations

This tool generates UUID v4 and UUID v7 only. It does not create name-based v3 or v5 UUIDs from a namespace and name, and it does not talk to a database to prove global uniqueness. UUID v7 uses your device clock; a wrong system time produces a wrongly ordered timestamp prefix. Generated values are identifiers, not credentials.

Common ways people use this generator

• Database primary keys

  Generate UUID v4 or v7 values for rows, documents, or event IDs without asking a server for the next sequence number.

• API request identifiers

  Create a unique request or correlation ID in the browser before you send a payload, then copy it into logs or headers.

• Test fixtures

  Generate a small batch of UUIDs for local fixtures, seed data, or mock responses. Nothing is uploaded.

• Time-ordered records

  Use UUID v7 when you want identifiers that roughly sort by creation time, such as event streams or append-only logs.

• Check an existing ID

  Paste a UUID from a log, token, or database dump to confirm it is well-formed and see which version it uses.

• Format conversions

  Toggle uppercase and hyphens on generated values when a system expects compact hex or uppercase GUIDs.

Frequently asked questions

What is a UUID generator?

A UUID generator creates Universally Unique Identifiers — 128-bit values usually written as 32 hexadecimal digits in 8-4-4-4-12 groups. This Toolshelf tool generates UUID v4 and UUID v7 in your browser and can validate a pasted UUID.

What is the difference between UUID v4 and UUID v7?

UUID v4 is random: almost all bits come from a cryptographically secure random source. UUID v7 is time-ordered: the first 48 bits are a Unix millisecond timestamp, and the remaining bits are random. Use v4 when you only need uniqueness. Use v7 when you also want values that sort by creation time.

Is this a random UUID generator?

Yes for version 4. UUID v4 generation prefers the browser’s crypto.randomUUID() function and otherwise uses crypto.getRandomValues(). The tool never uses Math.random(). UUID v7 is random after the timestamp prefix.

Are generated UUIDs unique?

A well-generated UUID v4 has 122 random bits, so accidental collisions are extraordinarily unlikely for normal use. UUID v7 uniqueness depends on the timestamp plus random bits. This page does not claim a mathematical guarantee across every device and clock.

Does this UUID generator store my values?

No. Generated UUIDs and validator input live only in page memory. They are not written to localStorage, cookies, or a database, and they disappear when you refresh or leave the page.

Is my UUID sent to a server?

No. Generation and validation run locally in JavaScript. Values are not posted to Toolshelf servers or third-party UUID APIs.

How do I validate a UUID?

Paste the value into the UUID validator. The tool accepts hyphenated, compact, uppercase, URN, and brace-wrapped forms. It reports whether the value is valid and which version nibble it contains.

Should I use a UUID as a password or secret?

No. A UUID is an identifier. UUID v7 even embeds a timestamp. Use a dedicated password generator when you need a secret.

Why is there a maximum of 500 UUIDs?

Large lists can slow the page if every value is rendered at once. The limit keeps accidental overload from a mistyped quantity in check. Generate another batch if you need more.

What UUID versions exist?

RFC 9562 defines versions 1 through 8. Version 1 and 6 are Gregorian time-based, 2 is DCE Security, 3 and 5 are name-based hashes, 4 is random, 7 is Unix time-ordered, and 8 is custom. This generator creates v4 and v7 and can detect the others when you paste a value.

Related guides

Short articles that explain the problem this tool solves.

• UUID v4 vs UUID v7 — UUID v4 is random. UUID v7 is time-ordered using a Unix millisecond timestamp plus random bits. See when to use each, how they look, and how to generate them in the browser.

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