Generate cryptographically random v4 UUIDs instantly with this free online UUID generator. Bulk generate up to 100 UUIDs at once, copy individually or all together with one click, and download as a text file. Options include uppercase formatting, hyphen removal, and wrapping in curly braces for GUID-style output. This tool uses your browser's native crypto.randomUUID() API — the gold standard for cryptographically secure random ID generation. All UUIDs are generated entirely in your browser. Nothing is sent to a server. Works offline, no signup required.
uuid-generator.tool
Generated UUIDs
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Frequently Asked Questions
What is a UUID?
A UUID (Universally Unique Identifier), also called GUID (Globally Unique Identifier), is a 128-bit identifier formatted as 32 hex digits in 5 groups: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. It is designed to be unique across distributed systems without a central coordinator. UUID is standardized in RFC 4122 and used in databases, APIs, file systems, and distributed architectures worldwide.
What is the difference between UUID v1, v4, and v5?
v1 — timestamp + MAC address. Unique but reveals when and where it was generated, which is a privacy risk.
v4 — 122 bits of pure randomness. The most commonly used version. No structure, no reversibility.
v5 — deterministic: given the same name and namespace, you always get the same UUID (uses SHA-1). Good for content-addressed identifiers.
v7 — new standard: timestamp-ordered v4. Solves index fragmentation in databases while keeping randomness.
Are v4 UUIDs truly unique?
Statistically, yes. A v4 UUID has 122 random bits. The probability of generating even a single collision requires producing approximately 2.71 quintillion UUIDs. For any real-world application, collisions are not a practical concern. This tool uses crypto.randomUUID() — a cryptographically secure random number generator — not Math.random().
UUID vs GUID — what is the difference?
They are the same format. GUID is Microsoft's term, used in Windows APIs, .NET, C#, and SQL Server. UUID is the RFC standard term, used in Linux, Java, Python, PostgreSQL, and most non-Microsoft ecosystems. Both are 128-bit identifiers in the same xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx format.
Should I use UUID as a database primary key?
UUIDs are excellent primary keys for distributed systems where you need to generate IDs on the client or across multiple services. Main benefits: globally unique, no ID enumeration attacks, client-generated. Main concern: random v4 UUIDs cause index fragmentation in MySQL/PostgreSQL B-tree indexes, which can harm write performance at scale. Solution: use UUID v7 (time-ordered) or ULID for high-write workloads.
How do I generate a UUID in JavaScript, Python, or Go?