UUID Generator Online — Free v4 & v1 UUID/GUID Maker
Generate UUID v4 (random) or v1 (timestamp) identifiers, one at a time or up to 100 at once, in standard, no-hyphen, uppercase, or braced format. Runs 100% in your browser — free, no signup.
Generator Options
Random UUIDs using cryptographically secure random numbers
Generate between 1 and 100 UUIDs at once
Generated UUIDs
Generated UUIDs will appear here...
Features
UUID v4 (Random)
Cryptographically secure random UUIDs
UUID v1 (Timestamp)
Time-based UUIDs with unique node ID
No Registration
100% free - no signup or account required
Bulk Generation
Generate up to 100 UUIDs at once
Multiple Formats
Standard, no hyphens, uppercase, or with braces
Instant Copy
One-click copy and download functionality
UUID Generator: Free v4 and v1 Unique Identifiers in Your Browser
A UUID generator creates 128-bit Universally Unique Identifiers — the standard way to key records without a central database authority. Pick v4 (random) or v1 (timestamp), set a count from 1 to 100, and choose standard, no-hyphen, uppercase, or braced output. v4 randomness comes from the Web Crypto API. It runs 100% in your browser, free, with no upload.
How to generate a UUID
- Choose a version: v4 (Random) for general-purpose IDs, or v1 (Timestamp) when you want time information embedded.
- Set the count to any value from 1 to 100 for single or bulk generation.
- Pick a format: standard lowercase with hyphens, no hyphens, uppercase, or braces
{uuid}for .NET/SQL Server. - Press Generate. Every UUID in the batch uses the version and format you selected.
- Use Copy per row, Copy All for the batch, or Download to save them as
toolk-uuids.txt.
What is a UUID and how does it work?
A UUID (also called a GUID in Microsoft tooling) is a 128-bit value written as 32 hexadecimal digits in five hyphen-separated groups: 8-4-4-4-12. Two of those digits are fixed by the spec — the 13th digit encodes the version and the 17th encodes the variant. The format and all versions are defined by RFC 9562, which was published in May 2024 and obsoleted the original RFC 4122 (2005).
UUID v4 fills 122 of its 128 bits with random data (6 bits are reserved for version and variant), giving 2122 ≈ 5.3 × 1036 possible values. This tool draws that randomness from the browser's Web Crypto API (crypto.getRandomValues), a CSPRNG — not the predictable Math.random(). UUID v1 encodes a 60-bit timestamp plus a node and clock sequence, so v1 values sort roughly by creation time. For new database keys that need to be sortable, RFC 9562 recommends the new time-ordered v7, which keeps B-tree indexes from fragmenting.
Worked examples: settings → output
v4 · standard format
3f2504e0-4f89-41d3-9a0c-0305e82c3301
Note the 4 in the 13th position (version) and 9 in the 17th (variant).
v4 · braces format (for .NET / SQL Server)
{3f2504e0-4f89-41d3-9a0c-0305e82c3301}
v4 · no-hyphens format
3f2504e04f8941d39a0c0305e82c3301
Edge case · CSPRNG vs Math.random fallback
v4 quality depends on the random source. In a normal browser this tool uses crypto.getRandomValues, which is cryptographically secure. Only if the Web Crypto API is missing (an old or stripped-down environment) does it fall back to Math.random() — a PRNG that is not safe for security tokens because its output can be predicted. Never use a Math.random()-based UUID as a session token or password-reset key; use a proper password generator instead.
UUID version reference
The versions defined by RFC 9562. This tool generates the two highlighted rows, v4 and v1; the others are listed so you can pick the right type for your stack.
| Version | Built from | Sortable? | Best for |
|---|---|---|---|
| v4 | 122 random bits (CSPRNG) | No | General-purpose IDs, public URLs, default choice |
| v1 | Timestamp + node + clock seq | Roughly | Legacy time-based IDs needing creation order |
| v3 / v5 | Hash of namespace + name (MD5 / SHA-1) | No | Deterministic IDs from the same input |
| v6 | Reordered v1 timestamp | Yes | Drop-in upgrade for sortable v1 |
| v7 | Unix ms timestamp + random | Yes | Modern database primary keys (recommended) |
The collision math, and the v1 privacy detail competitors skip
With 2122 possible v4 values, duplicates are a non-issue. By the birthday paradox you would have to generate about 2.71 quintillion (2.71 × 1018) UUIDs to reach even a 50% chance of a single collision — generating a billion per second, that takes roughly 85 years. That is why a 100-per-run cap (MAX_COUNT = 100) is plenty: collisions come from a weak random source, not from volume.
One real detail: the original RFC 4122 v1 used your network card's MAC address as the node, which leaked hardware identity. This tool instead generates a random 48-bit node with the multicast bit set — explicitly allowed by RFC 9562 — so the v1 UUIDs here carry a timestamp but expose no real MAC address.
Runs 100% in your browser
Your data never leaves your device. Every UUID is built locally in JavaScript and copied with your browser's native clipboard — no uploads, nothing leaves your device. I tested both v4 and v1 across all four formats at counts of 1, 10, and the hard cap of 100, and confirmed each output passes a strict UUID regex (correct version digit in position 13, variant in position 17). Generation and copy stayed instant even at 100 UUIDs.
Frequently asked questions
Is this UUID generator free?
Yes — 100% free with no signup and no daily cap beyond the 100-per-run limit. UUIDs are not copyrightable, so the output is free to use in personal and commercial projects.
Are my UUIDs sent to a server?
No. Generation happens entirely in your browser, with v4 randomness from crypto.getRandomValues. Nothing is uploaded or logged, so the tool works offline once the page has loaded.
Should I use v4 or v1?
Use v4 for almost everything — it is random and unpredictable. Use v1 only when you need a timestamp embedded in the ID. If you need sortable database keys, generate v7 in your data layer rather than relying on v1 ordering.
Can two UUID v4 values ever match?
Practically never. With 2122 possible values, you would need roughly 2.71 quintillion UUIDs to hit a 50% collision chance, so duplicates are not a realistic concern for any application.
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Last updated: June 2, 2026 · Runs 100% in your browser — no uploads, nothing leaves your device.
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