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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.
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) |
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 |
Formula & methodology
Formula: v4 UUID = 128 bits: 122 random + version (0100) + variant (10) bits, hex 8-4-4-4-12
- 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).
Frequently asked questions
What is a UUID?
A 128-bit universally unique identifier, written as 36 hex characters (8-4-4-4-12). Version 4 fills 122 bits with cryptographic randomness, making collisions practically impossible without any central registry.
Can two generated UUIDs collide?
Theoretically; practically no. You’d need to generate ~2.7×10¹⁸ v4 UUIDs for a 50% chance of one collision — billions per second for centuries.
When should I use v4 vs v7?
v4 for general identifiers. v7 embeds a timestamp so values sort by creation time — better as database primary keys (less index fragmentation). For most app-level IDs v4 remains the default.
Are these UUIDs generated securely?
Yes — via crypto.getRandomValues, the browser’s CSPRNG, entirely on your device. Nothing is fetched from or logged to a server.
Does removing hyphens break a UUID?
No — the 32 hex characters are the identity; hyphens are formatting. Many databases store them hyphen-less (or as 16 raw bytes). The option here just changes presentation.