UUID in Ruby

Ruby UUID Generator

Ruby's answer is one method from the standard library: SecureRandom.uuid, no gem involved.

Standard librarySecureRandom.uuiduuid_v7

Version

How many

Uppercase Hyphens Braces { }

Result

Generated locally with the Web Crypto API — nothing leaves your browser.

Generating UUIDs in Ruby

SecureRandom.uuid returns a version 4 UUID as a lowercase hyphenated string, sourced from the platform CSPRNG. It is part of securerandom, which ships with Ruby — so a Rails app needs no dependency to mint an identifier.
Newer releases of securerandom also provide SecureRandom.uuid_v7, which makes a time-ordered v7 value; that is the one to use as a primary key on a high-insert table, because sequential keys keep inserts at the end of the index. For storage, pair it with the right column type — PostgreSQL uuid, MySQL/ActiveRecord binary(16) — rather than a 36-character varchar.

How to generate

Press Generate UUID above to mint a value in this browser — nothing is sent anywhere.
Copy one value with Copy, or set How many and use Copy all for a fixture list.
Switch Version if your code needs v7 instead of the v4 default, and turn on Formatting to match your stack's conventions.

Use Cases

ActiveRecord primary keys — generate the ID in Ruby so the record knows it before save.
Public-facing tokens — reset links and API keys that must not be guessable from the next one.
Idempotency keys for Sidekiq jobs that can be retried.

How Ruby UUID Generator Compares

SecureRandom.uuid	v4, standard library, CSPRNG
SecureRandom.uuid_v7	v7, time-ordered — newer securerandom
SecureRandom.hex(16)	32 random hex characters — not a UUID, no version bits

Code Examples

Ruby

require "securerandom"

SecureRandom.uuid                # v4
# => "b8e2f1c0-3a7d-4e11-9c2d-1f0a6b7c8d9e"

SecureRandom.uuid_v7             # v7, time-ordered

# A batch for fixtures
Array.new(5) { SecureRandom.uuid }

ActiveRecord migration

create_table :orders, id: :uuid, default: "gen_random_uuid()" do |t|
  t.string :reference
  t.timestamps
end

# or, generating in Ruby:
class Order < ApplicationRecord
  before_create { self.id ||= SecureRandom.uuid }
end

Frequently Asked Questions

Do I need a gem to generate UUIDs in Ruby?

No — SecureRandom.uuid is in the standard library. A gem is only worth it if you also want parsing, validation or the other versions.

How do I get a UUID v7 in Ruby?

SecureRandom.uuid_v7, available in newer releases of the securerandom gem. On an older Ruby, use the uuid7 gem or generate it in PostgreSQL.

What column type should store a UUID in Rails?

On PostgreSQL, id: :uuid (16 bytes). On MySQL, binary(16). A varchar(36) works but wastes more than twice the space per row.