2026topopentools

UUID Generator

Generate one or many random version-4 UUIDs instantly, with options for uppercase and no hyphens.

UUID v4 is fully random, generated with the browser’s cryptographically secure random source.

Understanding the UUID Generator

This generator creates random version 4 UUIDs (universally unique identifiers) on demand. A UUID is a 128-bit value, written as 32 hexadecimal digits in the 8-4-4-4-12 pattern, used as a collision-resistant ID for database rows, API keys, files, and distributed systems. It is built for developers, DBAs, and testers who need unique identifiers without a central authority. Generate one or many at once, then copy them straight into code, seed data, or config.

How it works

Version 4 UUIDs are generated from random data. The tool calls the browser's Web Crypto API, crypto.randomUUID() or crypto.getRandomValues(), so the randomness comes from a cryptographically secure source, not Math.random(). It then fixes two fields the standard requires: the 13th hex digit is set to 4 (the version) and the 17th to 8, 9, a, or b (the variant). Everything runs locally in your browser, so no IDs are sent to a server or logged. Read each value left to right as the canonical lowercase string; uniqueness comes from the 122 random bits.

Worked example

A generated value looks like 3f2504e0-4f89-41d3-9a0c-0305e82c3301. The third group always starts with 4 (version 4) and the fourth group starts with 8-b (here, 9). With 122 random bits, you would need to generate roughly 2.71 quintillion UUIDs to reach a 50% chance of a single collision, so for practical purposes every value is unique. Generating 100 at once gives you 100 distinct IDs you can paste into a seed file.

Tips & common mistakes

  • Version 4 is random; do not expect any embedded timestamp or ordering. Use UUID v7 or a sortable key if you need time-based sorting.
  • Store UUIDs as a native uuid or 16-byte binary type in your database, not as a 36-character text column, to save space and speed up indexing.
  • UUIDs are not secret. Their randomness prevents guessing, but treat session tokens and passwords with purpose-built secrets, not bare UUIDs.
  • The canonical form is lowercase with hyphens; normalize case before comparing to avoid false mismatches.
  • Random v4 keys can fragment clustered indexes; consider this trade-off for high-write primary keys.

Related tools

JSON Formatter & ValidatorFormat, beautify, minify, and validate JSON with clear error messages.Base64 Encode / DecodeEncode text to Base64 or decode Base64 back to text, with full Unicode support.URL Encode / DecodePercent-encode or decode text for safe use in URLs and query strings.Hash GeneratorGenerate MD5, SHA-1, SHA-256, and SHA-512 hashes from any text.

Frequently Asked Questions

What is a UUID?

A UUID (Universally Unique Identifier), also called a GUID, is a 128-bit identifier that is practically guaranteed to be unique without a central authority. Version 4 UUIDs are random.

Are these UUIDs truly random?

Yes. They are generated with the browser's cryptographically secure random number generator (crypto.randomUUID), making collisions astronomically unlikely.

How many can I generate at once?

Up to 100 at a time. Use the Copy all button to grab the full list.