About this tool
A UUID (Universally Unique Identifier), also called a GUID (Globally Unique Identifier) in Microsoft environments, is a 128-bit label used to uniquely identify information in computer systems. The format is standardised by RFC 4122 (published by the IETF in 2005): eight hexadecimal characters, followed by three groups of four, and a final group of twelve, all separated by hyphens — resulting in a 36-character string like 123e4567-e89b-12d3-a456-426614174000.
UUID Version 4 (the type this generator produces) is generated using random or pseudo-random numbers. Two specific bits in the UUID are fixed to identify it as a v4 UUID (the version field is set to 4 and the variant field is set to binary 10). The remaining 122 bits are randomly generated. The theoretical number of possible UUID v4 values is 2^122, approximately 5.3 × 10^36. This makes the probability of generating a duplicate UUID effectively zero for all practical purposes — even if you generated one billion UUIDs per second for a century, the probability of a single collision would be less than one in a billion.
UUID v4 vs other versions: UUID v1 uses the current timestamp and the MAC address of the generating computer, which can expose information about when and where it was generated and is not suitable where anonymity matters. UUID v3 and v5 are deterministic — they hash a namespace and name to produce a consistent UUID. UUID v4 is the most widely used type for generating non-sequential, random, private identifiers for database keys, session tokens, and distributed system object identifiers.
This generator uses crypto.randomUUID() where available (Chrome 92+, Firefox 95+, Safari 15.4+) — the browser's native implementation of RFC 4122 UUID v4 generation. In older browsers, it falls back to generating random bytes using window.crypto.getRandomValues and manually constructing the UUID with the correct version and variant bits set. In both cases, generation is entirely client-side — no UUIDs are logged or transmitted.
Common uses for UUIDs: database primary keys (replacing sequential integer IDs to avoid enumeration attacks and to work in distributed systems without coordination); API resource identifiers; session tokens; file names for uploaded media (preventing filename collisions and guessing); distributed system message IDs; and Bluetooth device profiles, which use UUIDs defined in the Bluetooth specification to identify services and characteristics.
Practical Usage Examples
Database Primary Key
Standard hyphenated UUID v4, lowercase
Format: Hyphenated, Lowercase
Result: 550e8400-e29b-41d4-a716-446655440000Windows/COM GUID
Braced uppercase format used in legacy Windows systems
Format: Braced, Uppercase
Result: {550E8400-E29B-41D4-A716-446655440000}Step-by-Step Instructions
Set how many UUIDs you need — from 1 to 10,000.
Choose a format: Hyphenated (standard, e.g. 8-4-4-4-12) is most common; Compact removes hyphens; Braced wraps in {braces} for some Windows/COM systems; URN prefixes with "urn:uuid:".
Choose case: lowercase matches the RFC 4122 standard; uppercase is required by some legacy systems.
Click "Generate" to produce the UUIDs instantly using your browser's cryptographic random number generator.
Click Copy to copy all UUIDs to your clipboard, or Download to save them as a text file, one per line.
Core Benefits
Uses crypto.randomUUID() (native browser API) with a crypto.getRandomValues fallback for full RFC 4122 v4 compliance.
Generates up to 10,000 UUIDs per request for test data and bulk operations.
Supports all four standard formats: hyphenated, compact, braced, and URN.
100% client-side — UUIDs are generated in your browser and never transmitted or logged.
Free with no registration, no rate limits, and no usage caps.
Frequently Asked Questions
A UUID (Universally Unique Identifier) is a 128-bit label used to uniquely identify objects in computer systems. Standardised by RFC 4122, it is represented as a 32-character hexadecimal string separated by hyphens in the format 8-4-4-4-12 (e.g. 123e4567-e89b-12d3-a456-426614174000). UUID v4, the most common type, is generated using random numbers.
UUID (Universally Unique Identifier) and GUID (Globally Unique Identifier) are the same thing. GUID is the term used in Microsoft environments (COM, .NET, Windows), while UUID is the term used in the IETF standard (RFC 4122) and most other contexts. Both refer to the same 128-bit identifier format.
In practice, no. UUID v4 has 122 bits of randomness, giving 2^122 (approximately 5.3 × 10^36) possible values. The probability of generating a duplicate is negligible — if you generated one billion UUIDs per second for 100 years, the probability of any collision would still be less than one in a billion. For practical purposes, UUID v4 values are guaranteed unique.
UUID v1 is generated using the current timestamp and the MAC address of the generating machine, which makes it time-sortable but also potentially reveals when and where it was generated. UUID v4 is generated using random numbers, offering no such information leakage. UUID v4 is recommended for most modern applications where privacy and non-predictability matter.
Use the standard hyphenated format (8-4-4-4-12) unless your database or ORM has a specific requirement. PostgreSQL, MySQL, and most modern databases store UUIDs natively and efficiently. For compactness in storage, some systems store UUIDs as 16-byte binary values or 32-character hex strings without hyphens (compact format).
UUID v4 generates 128 random bits, then sets two specific fields to fixed values: the version field (bits 48–51) is set to 0100 (4 in hex) and the variant field (bits 64–65) is set to binary 10. The remaining 122 bits are random. This tool uses crypto.randomUUID() or crypto.getRandomValues to ensure cryptographically secure randomness.
URN (Uniform Resource Name) format prefixes the UUID with "urn:uuid:", resulting in a string like urn:uuid:123e4567-e89b-12d3-a456-426614174000. This format is used in XML namespaces, LDAP directories, and other contexts that require a URN-formatted identifier as defined in RFC 4122 and RFC 2141.
Yes, UUID v4 is safe to use as a public identifier for resources (e.g. in URLs like /users/123e4567-e89b-12d3-a456-426614174000). Because UUIDs are not sequential, they prevent enumeration attacks — unlike integer IDs where an attacker could simply increment the ID to discover other resources. Always combine with proper authentication and authorisation controls.
In modern browsers and Node.js 14.17+, use: crypto.randomUUID(). In older environments, you can use the "uuid" npm package: import { v4 as uuidv4 } from "uuid"; uuidv4();. Both produce a valid RFC 4122 UUID v4.
Use the built-in uuid module: import uuid; str(uuid.uuid4()). This produces a lowercase hyphenated UUID v4 string like "123e4567-e89b-12d3-a456-426614174000".
Yes. This tool supports bulk generation of up to 10,000 UUIDs in a single operation. The output is one UUID per line, which can be directly imported into spreadsheets, test data files, or databases.
Yes. This tool is completely free with no registration, no usage limits, and no premium tier. Generate as many UUIDs as you need.