Everytool

UUID Generator -Generate UUID v4, v1, v5 & ULID Online Free

A free online UUID generator. Instantly generate cryptographically secure UUIDs in all major versions (v4, v1, v5) and ULIDs. Generate single or bulk IDs, validate existing ones, and export to TXT or CSV.

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🔒 Trust and Privacy Notice: All UUID generation uses the Web Crypto API built into your browser. No UUIDs are ever sent to any server. All generation is completely local and private.

How to Generate a UUID

  1. Select your preferred UUID version from the tabs -v4 is recommended for most use cases
  2. A new UUID is generated automatically and displayed in the main panel
  3. Click Copy to copy it to your clipboard or New to generate another
  4. Use the Bulk Generator to generate multiple UUIDs at once -enter a count and click Generate
  5. Download the bulk results as a .txt or .csv file for use in your project

UUID Versions Explained

UUID v1 (Time-Based)

UUID v1 incorporates the current timestamp and a node identifier (usually a MAC address or random value). It's useful when you need identifiers that are sortable by creation time, though it can reveal timing and machine metadata.

UUID v4 (Random)

The most common version, v4 is generated using cryptographically secure random numbers. With 122 bits of randomness, the probability of collision is practically zero. It's the standard choice for most applications.

UUID v5 (Name-Based)

Deterministic UUIDs generated from a namespace and a specific name using SHA-1. The same inputs always produce the same UUID, making it perfect for consistent IDs across different systems without storage.

ULID (Sortable)

Universally Unique Lexicographically Sortable Identifier. It encodes a millisecond-precision timestamp followed by random characters. ULIDs are URL-safe and sort chronologically, which is excellent for database performance.

UUID vs GUID

GUID (Globally Unique Identifier) is Microsoft's name for UUID - they are the same standard (RFC 4122). GUIDs are typically displayed with surrounding braces in Windows and .NET contexts. This generator's Braces format output is compatible with GUID usage in .NET and SQL Server.

UUID in Database Design

UUIDs are widely used as database primary keys because they can be generated client-side without a database round-trip and are globally unique across distributed systems. The main advantage is the lack of coordination needed between nodes. However, random UUID v4 keys can cause index fragmentation in B-tree indexes as they are not sequential. For high-performance database indexing, it is highly recommended to use time-ordered IDs like ULID or UUID v7, which maintain the uniqueness of UUIDs while providing chronological sorting.

Key Features

  • UUID v4 (random), v1 (time-based), v5 (name-based), and ULID generation
  • Cryptographically secure via Web Crypto API
  • Bulk generate up to 1,000 UUIDs at once
  • Multiple output formats (lowercase, uppercase, no dashes, braces, URN)
  • Download as TXT or CSV
  • UUID validator with version and variant detection
  • UUID v1 timestamp decoder
  • Generation history for current session
  • Works on all devices including mobile
  • 100% free -no signup, no account, no data uploaded

Frequently Asked Questions

Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier) is a 128-bit identifier standardized by RFC 4122. It is represented as 32 hexadecimal digits in the format xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx. UUIDs are designed to be unique across space and time without requiring a central registry.

What is the difference between UUID v1 and UUID v4?

UUID v1 is time-based -it incorporates the current timestamp and a node identifier (usually a MAC address or random value) into the UUID. This means v1 UUIDs are sortable by creation time but can reveal timing information. UUID v4 is entirely random -it uses cryptographically secure random numbers with no embedded timestamp. v4 is the most widely used version because it is simpler and reveals no metadata.

What is UUID v5?

UUID v5 is a deterministic, name-based UUID generated using SHA-1 hashing. You provide a namespace UUID and a name string, and the same inputs always produce the same UUID output. This is useful when you need a consistent unique ID for a known resource -for example always generating the same UUID for a given URL or domain name.

What is a ULID?

A ULID (Universally Unique Lexicographically Sortable Identifier) is a 128-bit identifier that encodes a millisecond-precision timestamp in its first 10 characters and 16 random characters after. ULIDs sort chronologically, are URL-safe, and use Crockford's Base32 encoding. They are often preferred over UUIDs in databases where chronological ordering is important.

Is UUID v4 truly unique?

UUID v4 has 122 bits of randomness, giving approximately 5.3 undecillion possible values. The probability of generating two identical v4 UUIDs is astronomically small -to have a 50% chance of a collision you would need to generate over 2.7 quintillion UUIDs.

What is the difference between UUID and GUID?

GUID (Globally Unique Identifier) is Microsoft's term for the same concept as UUID. GUIDs follow the same RFC 4122 standard and are structurally identical to UUIDs. They are often displayed with surrounding braces in Windows and .NET contexts: {550e8400-e29b-41d4-a716-446655440000}.

Can I use UUIDs as database primary keys?

Yes, UUIDs are widely used as database primary keys because they can be generated client-side without a database round-trip and are globally unique across distributed systems. The tradeoff is that UUID v4 primary keys are random and can cause index fragmentation in some databases. UUID v7 (time-ordered) or ULIDs are better choices when index performance matters.

Is this UUID generator cryptographically secure?

Yes. This tool uses the Web Crypto API (crypto.randomUUID() and crypto.getRandomValues()) which provides cryptographically secure random number generation. All generation happens entirely in your browser -no UUIDs are sent to any server.

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