Generators

UUID Generator

Create v4 random or v7 time-ordered UUIDs in any quantity. Output is generated locally with the browser's crypto API — no upload, no signup, no rate limits.

UUID version122 cryptographically random bits. Use this when you need an opaque identifier with no time order.How manyFormat

Output

Private by design. UUIDs are generated locally with the browser's crypto API — your output is never sent to any server.

What is a UUID?

A UUID (Universally Unique Identifier), sometimes called a GUID, is a 128-bit value used to label things across systems without coordination. Two computers — or two services — can mint UUIDs at the same time and the chances of collision are vanishingly small, which is why UUIDs are everywhere: database primary keys, API request IDs, event IDs, file names, hardware identifiers, log correlation. The version number tells you how the bits were chosen. v4 is purely random and uncorrelated with anything else. v7 is the new standard for time-ordered IDs: the first 48 bits are a Unix-millisecond timestamp, the rest is random, so v7 IDs sort in creation order while keeping the collision-resistance of random bits.

How to generate UUIDs

1
Pick a version
v4 is the safe default for opaque identifiers. v7 is what you want when the IDs are going into a database index, log line, or sorted list and you would benefit from natural creation-time ordering.
2
Choose how many
Generate one for a quick paste, or up to 1,000 in a single batch for seed data, fixtures, or test inputs.
3
Pick a format
Standard with hyphens (xxxxxxxx-xxxx-...) is the right default. Use No hyphens for compact storage, Braces for legacy Microsoft GUIDs, or Uppercase to match a strict casing rule.
4
Copy or download
Click copy on a single row, Copy all to grab the whole batch, or Download .txt for a newline-separated file you can drop into a script.
5
Regenerate when needed
Every regenerate uses fresh entropy from window.crypto.getRandomValues. There is no caching of past values — once the page is closed, the IDs are gone.

How v4 and v7 are constructed

v4: 128 random bits, then version (4) and variant (10b) markers stamped into the canonical positions.
v7: high 48 bits = Unix milliseconds since epoch, then version (7), 12 random bits, variant (10b), 62 random bits.
Both are formatted as 8-4-4-4-12 lowercase hex, optionally with hyphens, braces, or uppercase casing.
Random bits are drawn from window.crypto.getRandomValues — a CSPRNG provided by the browser.
Version 4 has 122 bits of entropy; collision probability stays negligible up to many billions of IDs.
Version 7 has 74 bits of randomness per millisecond — enough to support trillions of IDs per millisecond per device without collision.

UUID layouts are defined by IETF RFC 9562 (which obsoleted the older RFC 4122). The version digit always sits at the start of the third group, and the variant bits sit in the high nibble of the fourth group — those two markers are how readers tell v4 from v7 from the legacy v1 and v3. v7 is the modern recommendation for new systems because its time prefix lets databases keep an index physically ordered by creation time, which dramatically improves cache locality and reduces page splits compared with the random shuffle that v4 produces.

Reference: RFC 9562 — Universally Unique Identifiers

Common formats

Format	Example
Standard v4	f81d4fae-7dec-41d0-a765-00a0c91e6bf6 8-4-4-4-12 hex with hyphens — the default everywhere.
No hyphens	f81d4fae7dec41d0a76500a0c91e6bf6 Compact form for URLs or fixed-length columns.
Braces (Microsoft GUID)	{f81d4fae-7dec-41d0-a765-00a0c91e6bf6} Common in COM, .NET, and Windows registry keys.
Standard v7	0190a4b8-9d4d-7e02-9f3a-7e9e7b5c1234 Sortable by time — newer IDs sort lexicographically after older ones.

When to use a UUID

Mint primary keys for distributed databases without round-tripping to a centralized sequence.
Tag API requests, log lines, and trace spans so they can be correlated across services.
Generate stable file or asset names that will not collide with concurrent uploads.
Seed test fixtures, mock data, or development databases with deterministic-looking but unique IDs.
Idempotency keys for billing, payment, or webhook delivery — same UUID = same intent.
Identify devices, sessions, or installations without leaking personally identifying information.
Build URL slugs that reveal nothing about creation order or count (use v4 for opacity).

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Frequently asked questions

Are these UUIDs really cryptographically random?

Yes. The randomness comes from window.crypto.getRandomValues, which every modern browser implements as a cryptographically secure pseudorandom number generator (CSPRNG). The output is suitable for security-sensitive use cases like idempotency keys or session tokens.

Should I use v4 or v7?

Use v7 if the IDs will end up in a database index, log file, or any list where creation-time ordering helps. The time prefix keeps the index physically sorted, which improves cache locality and reduces fragmentation. Use v4 when you specifically want IDs that do not leak when they were created — for example, public URL slugs.

What is the collision probability?

For v4, you would need to generate roughly 2.7 quintillion IDs before there is even a 50% chance of any single collision (the so-called birthday bound at 2^61). For v7, the time prefix changes every millisecond, so you would need to generate trillions of IDs in the same millisecond on the same device to even start worrying. Practical applications never come close.

Can I use these for security tokens?

v4 has 122 bits of entropy, which is enough for session IDs and CSRF tokens for most apps. For long-lived secrets that protect critical assets you should still prefer 256-bit random tokens (32 bytes from a CSPRNG) — UUIDs are convenient but not the highest-entropy option available.

Why is v7 better than v4 for databases?

Most relational databases store rows in primary-key order. With v4, every insert lands at a random position in the index, scattering pages all over disk and causing page splits. With v7, every new ID is greater than the last, so inserts append to the end of the index — far less I/O, far less fragmentation, and queries that filter on recent rows hit warm pages.

Are UUIDs sequential?

v4 is fully random — no order. v7 IDs are time-ordered to the millisecond: any two v7 IDs created in different milliseconds will sort in time order. Within the same millisecond, the random tail breaks ties, so the order is undefined but stable once minted.

Can the same UUID ever appear twice?

In principle yes, but the probability is so small it is not engineering-relevant. Distributed systems rely on UUIDs precisely because the math says coordination is unnecessary. If you ever do see a duplicate, the cause is almost always a buggy code path that reused a single value, not actual entropy collision.

Do I need to upload anything to use this tool?

No. The page generates UUIDs locally in your browser using window.crypto.getRandomValues. There is no network call, so the IDs are not visible to any server. Anything you generate stays on your device.

Last updated 2026-04-26

What is a UUID?

How to generate UUIDs

Pick a version

v4 is the safe default for opaque identifiers. v7 is what you want when the IDs are going into a database index, log line, or sorted list and you would benefit from natural creation-time ordering.

Choose how many

Generate one for a quick paste, or up to 1,000 in a single batch for seed data, fixtures, or test inputs.

Pick a format

Standard with hyphens (xxxxxxxx-xxxx-...) is the right default. Use No hyphens for compact storage, Braces for legacy Microsoft GUIDs, or Uppercase to match a strict casing rule.

Copy or download

Click copy on a single row, Copy all to grab the whole batch, or Download .txt for a newline-separated file you can drop into a script.

Regenerate when needed

Every regenerate uses fresh entropy from window.crypto.getRandomValues. There is no caching of past values — once the page is closed, the IDs are gone.

How v4 and v7 are constructed

v4: 128 random bits, then version (4) and variant (10b) markers stamped into the canonical positions.
v7: high 48 bits = Unix milliseconds since epoch, then version (7), 12 random bits, variant (10b), 62 random bits.
Both are formatted as 8-4-4-4-12 lowercase hex, optionally with hyphens, braces, or uppercase casing.
Random bits are drawn from window.crypto.getRandomValues — a CSPRNG provided by the browser.
Version 4 has 122 bits of entropy; collision probability stays negligible up to many billions of IDs.
Version 7 has 74 bits of randomness per millisecond — enough to support trillions of IDs per millisecond per device without collision.

Common formats

Format	Example
Standard v4	f81d4fae-7dec-41d0-a765-00a0c91e6bf6 8-4-4-4-12 hex with hyphens — the default everywhere.
No hyphens	f81d4fae7dec41d0a76500a0c91e6bf6 Compact form for URLs or fixed-length columns.
Braces (Microsoft GUID)	{f81d4fae-7dec-41d0-a765-00a0c91e6bf6} Common in COM, .NET, and Windows registry keys.
Standard v7	0190a4b8-9d4d-7e02-9f3a-7e9e7b5c1234 Sortable by time — newer IDs sort lexicographically after older ones.

When to use a UUID

Mint primary keys for distributed databases without round-tripping to a centralized sequence.

Tag API requests, log lines, and trace spans so they can be correlated across services.

Generate stable file or asset names that will not collide with concurrent uploads.

Seed test fixtures, mock data, or development databases with deterministic-looking but unique IDs.

Idempotency keys for billing, payment, or webhook delivery — same UUID = same intent.

Identify devices, sessions, or installations without leaking personally identifying information.

Build URL slugs that reveal nothing about creation order or count (use v4 for opacity).