UUID & GUID Generator
100% privateFree online UUID & GUID generator — create random UUID v4 instantly. Bulk generate up to 100, toggle uppercase, one-click copy. 100% browser-based.
f0edc76e-ef39-4f8d-b852-775d0b659176This free online UUID generator creates cryptographically random UUID version 4 identifiers using the browser-native crypto.randomUUID() API — the same CSPRNG source used by operating systems and security libraries. UUID v4 is the most widely used format for database primary keys, session tokens, distributed trace IDs, and anywhere a unique identifier is needed without a central coordination service. Generate one UUID or bulk-generate up to 100 in a single click.
UUID and GUID refer to the same 128-bit identifier — GUID (Globally Unique Identifier) is simply Microsoft's name for UUID, used in .NET, C#, SQL Server, and COM. This online GUID generator produces identifiers compatible with Guid.NewGuid() in C#, New-Guid in PowerShell, UUID.randomUUID() in Java, and uuid.uuid4() in Python. Toggle uppercase output to match .NET conventions, or keep lowercase for Linux, Node.js, PostgreSQL, and most RFC 4122-compliant systems.
Whether you need a random UUID generator online, a GUID generator for SQL Server insert scripts, a Python UUID generator alternative, a Java UUID generator, or a JavaScript UUID generator replacing the uuid npm package, this tool gives you production-safe identifiers in your browser — no libraries, no backend, no rate limits. All generation uses the system cryptographic random source with 122 bits of entropy per UUID.
How It Works
- Choose how many UUIDs to generate (1 to 100) using the quantity input
- Click Generate — each UUID is produced using crypto.randomUUID(), a cryptographically secure source backed by the OS CSPRNG
- Toggle uppercase if your system (e.g. .NET, SQL Server) uses uppercase GUID format
- Copy individual UUIDs or the entire batch with one click — nothing is sent to any server
Features
- UUID v4 generation using crypto.randomUUID() (cryptographically secure CSPRNG)
- GUID-compatible output for .NET, C#, SQL Server, and COM systems
- Bulk generation: 1 to 100 UUIDs per click
- Uppercase toggle for .NET / Microsoft systems; lowercase for RFC 4122 standard
- One-click copy for individual UUIDs or the full batch
- 100% browser-based — no server, no tracking, no rate limits
- Works offline after the first page load
Examples
UUID v4 (lowercase — RFC 4122 standard)
Input
Generate 1 UUIDOutput
f47ac10b-58cc-4372-a567-0e02b2c3d479GUID (uppercase — .NET / SQL Server format)
Input
Generate 1 GUID (uppercase)Output
F47AC10B-58CC-4372-A567-0E02B2C3D479Bulk generation (5 UUIDs)
Input
Generate 5 UUIDsOutput
a3bb189e-8bf9-3888-9912-ace4e6543002
1b9d6bcd-bbfd-4b2d-9b5d-ab8dfbbd4bed
3cf99b56-2c79-4e28-ae15-bceead5c3d42
e0a1b2c3-d4e5-4f60-a7b8-c9d0e1f20001
9f8e7d6c-5b4a-4392-8817-a6b5c4d3e2f1Common Use Cases
- Generating database primary keys for PostgreSQL (uuid type), MySQL (CHAR(36)), and SQL Server (uniqueidentifier)
- Creating unique IDs for distributed systems and microservices without a central counter or sequence
- Producing GUIDs for .NET, C#, and SQL Server insert scripts (uppercase format)
- Generating trace IDs and correlation IDs for distributed system observability (OpenTelemetry, Jaeger)
- Replacing uuid.uuid4() in Python, UUID.randomUUID() in Java, or the uuid npm package in Node.js for quick one-off generation
Developer Tips
- crypto.randomUUID() is built into all modern browsers and Node.js 14.17+ — you often do not need the uuid npm package for UUID v4 generation
- UUID v4 is not sortable — if you need time-ordered unique IDs for database clustered index locality, consider UUID v7 or ULID instead
- In PostgreSQL, store UUIDs as the uuid native type (16 bytes), not VARCHAR(36) (36 bytes) — it is more compact and supports equality index scans natively
- Minecraft offline-mode UUIDs are name-based (UUID v3, derived from the player name) — UUID v4 from a random generator will not match a Minecraft offline UUID
Frequently Asked Questions
- What is a UUID generator?
- A UUID generator is a tool or function that produces Universally Unique Identifiers — 128-bit values formatted as five groups of hexadecimal digits separated by hyphens (xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx). UUID generators are used to create unique primary keys for databases, session tokens, trace IDs, and any identifier that must be globally unique without a central coordination service. UUID v4 generators use a cryptographically secure random source, giving 2^122 possible values.
- What is the best UUID generator for developers?
- The best UUID generator for developers uses a cryptographically secure random source (not Math.random()), runs in the browser without sending data to a server, supports bulk generation, and produces output compatible with all platforms. This tool uses the browser-native crypto.randomUUID() API — the same CSPRNG used by operating systems — and supports both lowercase UUID (RFC 4122) and uppercase GUID (.NET, SQL Server) formats with one-click copy.
- How does a UUID generator work?
- A UUID v4 generator works by filling 128 bits with cryptographically random data from the OS CSPRNG (/dev/urandom on Linux, CryptGenRandom on Windows). Specific bits are then set to mark the version (bits 12–15 of the third group are set to 0100 for version 4) and the RFC 4122 variant (bits 6–7 of the fourth group are set to 10). The resulting 128 bits are formatted as five hyphen-separated groups of hexadecimal digits, producing the familiar xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx pattern.
- What is a UUID?
- A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in software systems. The standard format is five groups of hexadecimal digits separated by hyphens: xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are used as database primary keys, session tokens, transaction IDs, and anywhere a unique identifier is needed without central coordination. The RFC 4122 standard defines five UUID versions; v4 (random) is the most widely used.
- What is the difference between UUID v4 and other versions?
- UUID v4 is randomly generated, making it the most common version for general application use. UUID v1 is time-based and encodes the MAC address of the generating machine — a privacy concern in some contexts. UUID v3 and v5 are name-based and deterministic (used for consistent IDs derived from a namespace and name, such as Minecraft offline-mode player UUIDs). UUID v7, a newer version, is time-ordered and random — useful for database primary keys where sort order matters for index performance.
- Are the generated UUIDs truly unique?
- Yes, in practice. UUID v4 uses 122 bits of randomness, giving 2^122 possible values — approximately 5.3 × 10^36. The probability of generating the same UUID twice, even across one trillion UUIDs per second for a billion years, is negligibly small. For all practical applications, UUID v4 collisions can be treated as impossible.
- Is it safe to use these UUIDs in production?
- Yes. This tool uses the browser's crypto.randomUUID() API, which is backed by the OS cryptographically secure pseudorandom number generator (CSPRNG). This is the same randomness source used by security libraries and operating systems. The generated UUIDs are suitable for database primary keys, file names, session identifiers, API keys, and other production use cases.
- What is the difference between a UUID and a GUID?
- UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) refer to the same 128-bit identifier format. GUID is Microsoft's term, used in .NET, C#, SQL Server, COM, and Windows APIs. UUID is the term defined in RFC 4122. Both use the same structure and uniqueness guarantees. The only common difference is formatting convention: Microsoft systems often use uppercase GUIDs, while Unix and RFC 4122-compliant systems use lowercase UUIDs.
- Can I use lowercase or uppercase UUIDs?
- Both are valid. The RFC 4122 standard specifies lowercase hexadecimal digits, and most Unix, Linux, and web systems generate lowercase UUIDs. UUID comparison is case-insensitive per the standard, so uppercase GUIDs are equally valid. .NET's Guid.NewGuid().ToString("D") produces uppercase by default. Use the uppercase toggle on this tool to match your system's convention.