UUID Generator: Generate IDs Online
Generate UUID values for sample records and application development. Choose a supported mode and inspect the output before using it as an identifier.
UUID Generator workspace
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)
Simplified timestamp-based output; review interoperability limits
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
Generate UUID v4 Values and Understand Timestamp Mode
Generate UUID values for sample records and application development. Choose a supported mode and inspect the output before using it as an identifier. Random UUIDs are identifiers, not access controls. This implementation also includes a simplified timestamp-based mode, which should not be treated as proof of full UUID version 1 interoperability. Use a standards-tested library when a system requires a particular UUID version.
How to use the UUID generator
- Choose a version: v4 (Random) for general-purpose IDs, or v1 (Timestamp) for simplified sample values only.
- 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 positions carry format information — 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) when available, with a weaker Math.random() fallback otherwise. Standard UUID v1 uses a timestamp, node and clock sequence; this tool implements only a simplified timestamp mode. For time-ordered identifiers, evaluate a standards-tested UUID v7 implementation in your application.
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. Do not use these identifiers as session tokens or password-reset keys. Generate those secrets through your authentication framework.
UUID version reference
The versions defined by RFC 9562. This tool offers v4 and a simplified mode labeled v1; the v1 row describes the standard, not a compliance claim for this implementation. Use this comparison when selecting a library 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 | Not in standard text order | Legacy systems requiring UUID v1 |
| 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) |
Randomness, uniqueness and timestamp-mode limits
A v4 UUID has 122 random bits. Collision estimates assume independent, uniformly random generation; they are not a guarantee that every identifier is unique. Keep database uniqueness constraints and retry on conflicts. The 100-value batch limit is an interface limit, not a security property.
This tool does not read a hardware MAC address. Its timestamp mode uses Date.now() and random node bytes, rather than the complete RFC version 1 algorithm. Use it for sample data only; choose a verified implementation when exchanging version 1 identifiers with other systems.
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Last updated: September 15, 2026 · Runs 100% in your browser — no uploads, tool input is not sent to Toolk.
Frequently asked questions
Which UUID versions does this generator produce, and which should I choose?
Choose v4 for random sample identifiers. The option labeled v1 is a simplified timestamp-based implementation, not a fully interoperable RFC 9562 version 1 generator. Use a standards-tested library for systems that require a particular UUID version or time-ordered database keys.
Do the v1 UUIDs here leak my MAC address like old implementations did?
The timestamp mode generates random node bytes; it does not read your network card MAC address. Its timestamp and node handling are simplified, so do not treat this mode as a standards-compliant UUID v1 implementation.
Are generated UUIDs transmitted or stored anywhere?
Generation runs locally in JavaScript. The tool does not submit generated identifiers to Toolk. Web Crypto supplies randomness when available; environments without it use a weaker Math.random fallback. Page analytics are separate from identifier generation.
Can a UUID v4 collide with an existing record?
Collisions are possible. With independent, uniformly random v4 values, the 122 random bits make accidental collisions unlikely at ordinary application volumes. That assumption does not justify a uniqueness guarantee, and the Math.random fallback is unsuitable for secrets. Enforce uniqueness in your database and generate security tokens in a suitable authentication library.