UUID / GUID Generator

Generate UUID v4 (random) and v7 (time-ordered) locally in your browser. Batch copy, formatting options, no server.

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Why v4 & v7 Only

What Most Developers Use

UUID v4 is the usual default: random, simple, and supported everywhere. UUID v7 (RFC 9562) is increasingly chosen for database primary keys because values are roughly time-ordered, which helps index locality and sequential access. This tool exposes only those two because they cover the vast majority of day-to-day needs.

Other Versions (v1, v3, v5, v6)

v3 and v5 are deterministic: the same namespace and name always yields the same UUID—great for stable internal IDs, not for generating many independent random IDs. v1 and v6 are mostly legacy or niche; new systems that want time-ordering often pick v7 instead. v2 is specialized and rarely used in general apps.

Mastering UUID Versions

Which Version Should I Use?

Choose v4 when you need unpredictable IDs with no ordering guarantee. Choose v7 when creation time should roughly match sort order (for example, clustered indexes or time-range queries). Both are suitable for public-facing identifiers.

What is UUID v7?

UUID v7 combines a Unix epoch timestamp with random bits (per RFC 9562). Unlike v4, v7 values are naturally sortable by creation time, which can improve behavior in databases such as PostgreSQL and MySQL compared to fully random UUIDs.

Is It Cryptographically Strong?

Yes. Generation runs entirely in your browser using the uuid package, which uses cryptographically secure randomness from the Web Crypto stack where available. Nothing is sent to our servers.

Formatting & Best Practices

Hyphens vs. Hex Strings

Standard UUIDs are 36-character strings with 4 hyphens. Many modern databases (like MongoDB) or storage-efficient systems prefer the "No Hyphens" (32-character hex) format to save space and simplify indexing.

Case Sensitivity

While UUIDs are technically case-insensitive hex strings, some legacy systems require UPPERCASE while modern web standards (like JSON API) prefer lowercase. You can switch between them instantly in our tool.

Privacy & Security

On LeetTools.dev, 100% of the generation happens in your browser. No data is transmitted to our servers. This is critical when generating IDs for sensitive system architectures or private user records.