Implements UUID v4 (RFC 4122) using window.crypto.getRandomValues(). You get 122 random bits plus 6 fixed bits for version and variant. The format is the familiar 8-4-4-4-12 (36 characters with hyphens) or you can drop the hyphens for compact 32-character storage. Collision probability is basically zero—we're talking 1 in 5.3×10^36, so you're good.
UUID Generator
Generate random UUID v4 identifiers instantly. Support for bulk generation, various formats, and one-click copy. Free online UUID generator.
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Frequently Asked Questions
Quick answers to common questions
What is a UUID and how is its structure defined by RFC 4122?
A UUID (Universally Unique Identifier), also known as a GUID (Globally Unique Identifier), is a 128-bit identifier standardized by RFC 4122 and used to uniquely identify information in computer systems without central coordination. The standard 8-4-4-4-12 format displays as 123e4567-e89b-12d3-a456-426614174000, where: 8 digits (time_low), 4 digits (time_mid), 4 digits (time_hi_and_version), 4 digits (clock_seq_hi_and_reserved + clock_seq_low), and 12 digits (node). The version digit (1-5) indicates the UUID variant, while the variant bits (typically 10xx binary) indicate the UUID variant. UUID v4, the most common version, uses 122 random bits (version 4 and variant 10xx consume 6 bits, leaving 122 for randomness), generated using cryptographically secure random number generators. This structure ensures uniqueness across space and time without requiring registration with a central authority.
What are the different UUID versions and when should I use v1, v4, or v5?
UUID has several versions, each with different generation methods: v1 (time-based) combines the MAC address of the generating computer with a 60-bit timestamp and 100-nanosecond precision, plus random bits—this makes it sortable by creation time but leaks the MAC address (privacy concern). v3 (MD5-based) and v5 (SHA-1 based) are deterministic, generated by hashing a namespace UUID with a name—the same input always produces the same UUID, useful for consistent identifiers from known strings. v4 (random) uses 122 random bits, ideal for most applications requiring uniqueness without coordination. v7 (time-ordered, newer) combines timestamp with random bits for sortable random UUIDs. Recommendation: Use v4 for general purpose (database keys, request IDs), v5 when you need deterministic IDs from names, and avoid v1 due to privacy concerns. Our tool generates v4, the most widely supported and privacy-preserving version.
How unique are UUIDs and what is the collision probability?
UUID v4 provides 122 random bits, resulting in 5.3×10^36 (2^122) possible combinations. To put this in perspective: you'd need to generate 1 billion UUIDs per second for 85 years before having a 50% chance of collision, and even then, you'd need to store all 2.7×10^18 generated UUIDs to detect the collision. For practical purposes, UUID collisions are impossible—the birthday paradox means collisions become theoretically likely only after generating 2.3×10^18 UUIDs (approximately 2.3 quintillion). By comparison, the Earth has an estimated 10^50 atoms, making UUID space vastly smaller but still practically infinite for human-scale applications. For database applications with billions of records, UUIDs provide sufficient uniqueness guarantees. If you're concerned about collisions (e.g., systems with trillions of records), consider using UUID v7 or adding a database-specific prefix to further reduce collision probability.
How do I generate UUIDs in different programming languages and integrate them?
Most programming languages have built-in UUID support. JavaScript: `crypto.randomUUID()` (modern browsers/Node.js) returns v4 UUIDs, or use libraries like `uuid`. Python: `import uuid; uuid.uuid4()` generates v4, `uuid.uuid5(namespace, name)` for v5. Java: `java.util.UUID.randomUUID()` returns v4. C#: `Guid.NewGuid()` creates GUIDs (Microsoft's UUID equivalent). PHP: `uuid_create(UUID_TYPE_RANDOM)` or `ramsey/uuid` library. Go: `github.com/google/uuid` package. Ruby: `require 'securerandom'; SecureRandom.uuid` for v4. SQL databases: PostgreSQL `gen_random_uuid()` (extension `pgcrypto`), MySQL `UUID()`, SQL Server `NEWID()`. When integrating: ensure your database columns accept 36-character strings (with hyphens) or 16-byte binary types for storage efficiency. For APIs, transmit UUIDs as lowercase strings without braces for maximum compatibility. Always validate UUID format using regex: `/^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i` for v4.
Can I generate UUIDs in bulk and what are the use cases for batch generation?
Yes! Our tool supports bulk UUID generation—generate up to 1000 UUIDs at once by specifying the quantity. This is essential for several use cases: 1) Database seeding—populate test databases with realistic unique identifiers for development and testing. 2) Data migration—assign new UUIDs to existing records when migrating from systems with auto-increment IDs. 3) Batch processing—generate UUIDs for CSV imports, bulk API requests, or ETL pipelines. 4) Load testing—create thousands of unique entities for performance testing without ID collisions. 5) Distributed systems—pre-generate UUID batches for services that can't afford generation overhead during high-traffic periods. The tool outputs UUIDs in a text format (one per line or comma-separated), easily copied into spreadsheets, SQL scripts, or configuration files. Bulk generation is faster than generating one-by-one and ensures uniqueness within the batch through our CSPRNG implementation.
What format options are available for UUIDs and how do I choose between them?
UUIDs can be formatted in several ways depending on your use case: 1) Standard format (8-4-4-4-12): `123e4567-e89b-12d3-a456-426614174000` with hyphens—most common, human-readable, RFC 4122 compliant. 2) Compact format (32 hex digits): `123e4567e89b12d3a456426614174000` without hyphens—useful for URL paths, compact storage, or when hyphens cause parsing issues. 3) Uppercase vs lowercase: UUIDs are case-insensitive (hexadecimal), but lowercase is preferred for URLs and JSON, while uppercase is sometimes used in Windows environments. 4) Braced format: `{123e4567-e89b-12d3-a456-426614174000}`—required by some Windows applications and .NET GUID representations. 5) URN format: `urn:uuid:123e4567-e89b-12d3-a456-426614174000`—used in XML namespaces and formal specifications. Our tool provides options for all these formats. Recommendation: Use standard lowercase with hyphens for most applications, compact without hyphens for URLs and storage-constrained systems, and braced only when required by specific software.
Are UUIDs secure for use in URLs and as authentication tokens?
UUID v4 generated with cryptographically secure random number generators (CSPRNG, like our tool uses) is sufficiently random for most security applications, but there are important caveats. For URLs: UUIDs are safe as resource identifiers (e.g., `/api/users/123e4567-e89b-12d3-a456-426614174000`) because they don't reveal sequential patterns—unlike auto-increment IDs, which allow enumeration attacks (trying `/api/users/1`, `/users/2`, etc.). However, UUIDs are not authentication tokens or session IDs by themselves—don't use them as password reset tokens or API keys without additional cryptographic signing, as the generation algorithm is public and predictable if the CSPRNG is compromised. For session management, frameworks often use UUID v4 combined with server-side state. For password reset tokens, use cryptographically signed tokens (JWT) or UUIDs stored with expiration timestamps in a secure database. For anonymity, UUID v4 is preferable to v1 (which leaks MAC address and generation time). Our tool uses Web Crypto API's CSPRNG, providing cryptographic randomness suitable for security-critical applications.
Is my UUID generation private and secure when using this online tool?
Your privacy and security are guaranteed: all UUID generation happens entirely within your browser using client-side JavaScript and the Web Crypto API. No data is ever sent to any server—no generated UUIDs, no configuration settings, no usage analytics, no cookies, no tracking. The entire generation process runs locally on your device using `crypto.randomUUID()`, which performs cryptographically secure random number generation without network access. You can verify this by disconnecting from the internet—the tool continues working perfectly because it requires no network connection. Additionally, our website is served over HTTPS with strict transport security (HSTS), ensuring the tool itself hasn't been tampered with during transmission. Since UUIDs are randomly generated and don't contain personal information, there's no privacy risk from the UUIDs themselves—we can't see them even if we wanted to. For maximum security in sensitive environments, consider that browser extensions might theoretically access generated content, though this is unlikely. We recommend clearing the output field after copying sensitive UUIDs if working in a shared environment.
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Use Cases
Discover how to integrate this tool into your workflow
Database Design
Generate unique identifiers for database records and entities.
- Primary key generation
- Record identification
- Distributed systems
- Data migration
API Development
Create unique request IDs and resource identifiers.
- Request tracking
- Resource naming
- Session identification
- Transaction IDs
Application Logging
Generate unique IDs for log entries and correlation.
- Log correlation
- Distributed tracing
- Error tracking
- Audit trails
About This Tool
UUIDs are boring but necessary. This tool generates UUID v4 (the random kind) which is what 99% of people mean when they say "UUID". Generate one or a hundred at a time—bulk mode is clutch when you're seeding a database or need a bunch of test IDs. Standard format with hyphens or without (compact), depending on whether you're storing it in a database or displaying it.
Technical Details
Algorithm
Random bits from CSPRNG, formatted according to RFC 4122. Version 4 means "random UUID" as opposed to UUID v1 (MAC-based) or v3/v5 (namespace-based). Most people just need v4, which is what this generates. Simple, effective, collision-resistant enough that you'll never have to worry about it in practice.
Privacy Commitment
🔒 **Privacy First**: Unlike server-based tools, AI-TOL processes everything locally in your browser - your data never leaves your device. No uploads, no tracking, completely private.