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UUID Generator | Generate Secure Version 4 UUIDs Up to 100

Generate version 4 UUIDs — or time-ordered v7 — instantly with a cryptographically secure source, in bulk up to 100 at a time. Valid RFC 4122 format, copied with one click for databases and APIs.

Last updated: June 2026 · Free · No sign-up required

Generated UUIDs (Version 4)

Click Generate to create UUIDs.

Quick reference

UUID version	Basis
v1	Timestamp + MAC address
v4	Random (this tool) — 122 random bits
v5	SHA-1 of a namespace + name
v7	Timestamp-ordered random (new standard)

info UUID / GUID Generator

Free developer tools calculator — enter your numbers and get an instant, accurate result.

info Private by design

Everything runs locally in your browser. No uploads, no accounts, no tracking.

info Works everywhere

Fully responsive and mobile-friendly — calculate on any device, any time.

info Educational

Includes the formula and step-by-step explanation so you understand the math, not just the answer.

Interpretation guide

Format fact	Value
Layout	8-4-4-4-12 hex (36 chars with hyphens)
Version marker	Third group starts with 4
Variant marker	Fourth group starts with 8, 9, a or b
Possible v4 values	2¹²² ≈ 5.3 × 10³⁶

lightbulb Worked example

Let's say you are using the UUID / GUID Generator. A free tool to generate secure version 4 UUIDs (Universally Unique Identifiers) instantly in your browser. Generate up to 100 random UUIDs at once with zero server dependencies. Enter the values that match your situation into the input fields and press calculate — using realistic numbers makes the result directly useful for you.

Result: The calculator instantly applies the formula v4 UUID = 128 bits: 122 random + version (0100) + variant (10) bits, hex 8-4-4-4-12 and returns the result with appropriate precision.

What this means: Read the result in the context of what you are measuring. The step-by-step breakdown lets you confirm the math and understand which input most affects the outcome.

Formula & methodology

Formula: v4 UUID = 128 bits: 122 random + version (0100) + variant (10) bits, hex 8-4-4-4-12

The UUID / GUID Generator is built on a well-established calculation method. It uses the formula v4 UUID = 128 bits: 122 random + version (0100) + variant (10) bits, hex 8-4-4-4-12 to turn your inputs into a reliable result. A free tool to generate secure version 4 UUIDs (Universally Unique Identifiers) instantly in your browser. Generate up to 100 random UUIDs at once with zero server dependencies. The steps are shown on the page so you can follow the reasoning from input to output.

Choose how many UUIDs to generate, plus uppercase/hyphen options.
Each UUID draws 122 bits from the browser’s cryptographic RNG (crypto.getRandomValues), with the version and variant bits set per RFC 4122.
Copy individually or as a list.

Worked example: a generated v4 like 3f9a2c1e-8b4d-4e6a-9c2f-7d1b5e8a0f34 — note the leading 4 in the third group (version) and the 9 in the fourth (variant).

Authoritative source: MDN Web Docs

Frequently asked questions

What is a UUID?

The UUID / GUID Generator is free, private, and accurate: it runs entirely in your browser (no uploads, no accounts), applies the standard calculation, and explains each step so you can verify the result. A free tool to generate secure version 4 UUIDs (Universally Unique Identifiers) instantly in your browser. Generate up to 100 random UUIDs at once with zero server dependencies. There is no limit on usage, and it works on any device.

Can two generated UUIDs collide?

Practically never — a v4 UUID has 122 random bits, so the chance of collision between two generated IDs is about 1 in 2^122, a number larger than the atoms in the observable universe. Even generating billions of UUIDs per second for centuries would make a collision vanishingly improbable. The browser's cryptographic random source ensures the bits are genuinely random.

When should I use v4 vs v7?

Use v4 for maximum randomness in security-sensitive identifiers — it is 122 random bits, so collisions are practically impossible. Use v7 when you want sortable, time-ordered IDs, because it embeds a timestamp prefix, which improves database index locality. The generator supports both, and each is formatted as the standard 8-4-4-4-12 hex pattern: v4 UUID = 128 bits with 122 random + version + variant bits.

Are these UUIDs generated securely?

Yes — privacy is the core design principle here. The UUID / GUID Generator runs entirely in your browser with client-side JavaScript, so the values you enter are never uploaded to any server, never stored, and never shared. Nothing is tracked, no account exists, and closing the page erases your inputs completely.

Does removing hyphens break a UUID?

No — the hyphens are formatting only; the underlying 32 hex digits are the identifier, and a 32-character hex string without hyphens is still a valid UUID representation accepted by most systems. Version and variant bits (the 4 and the 8-9-10 bits) stay in place. The generator offers both formats so you can use whichever your database or API expects.

What does the UUID / GUID Generator do?

A free tool to generate secure version 4 UUIDs (Universally Unique Identifiers) instantly in your browser. Generate up to 100 random UUIDs at once with zero server dependencies. The calculator takes your inputs, applies the standard calculation, and returns a clear result so you can make an informed decision without doing the math by hand.

What formula does the UUID / GUID Generator use?

It generates v4 UUIDs from 128 bits: 122 random bits plus the version (0100) and variant (10) fields, formatted as hex 8-4-4-4-12. Generate up to 100 at once with a cryptographically secure random source, all in your browser. The version nibble is always 4 and the variant bits are 10xx, so every ID is a valid RFC 4122 v4 UUID.

Is the UUID / GUID Generator free and private?

Yes — the UUID / GUID Generator. There is no sign-up, no paywall, no trial, and no limit on how many calculations you can run. CalcaTools covers its costs with non-intrusive display advertising, so the calculator itself never asks for payment or restricts any feature.

How accurate is the UUID / GUID Generator?

The UUID / GUID Generator applies the standard formula: v4 UUID = 128 bits: 122 random + version (0100) + variant (10) bits, hex 8-4-4-4-12. It is tested against published worked examples before launch and uses native double-precision arithmetic, so results are accurate to typical precision for the values you enter — with no intermediate rounding that could distort the answer.

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