Generate UUID in Ruby

UUID v4 - Random (built-in stdlib)

require 'securerandom'

# Returns a lowercase hyphenated string - no object wrapping
id = SecureRandom.uuid
# → "550e8400-e29b-41d4-a716-446655440000"

UUID v5 - Deterministic (UUIDTools gem)

# gem install uuidtools
require 'uuidtools'

# SHA-1 hash of namespace + name - same inputs always produce the same UUID
id = UUIDTools::UUID.sha1_create(UUIDTools::UUID_DNS_NAMESPACE, 'example.com')
puts id.to_s # → always "cfbff0d1-9375-5685-968c-48ce8b15ae17"

Rails - ActiveRecord UUID primary key

# config/initializers/generators.rb
Rails.application.config.generators do |g|
  g.orm :active_record, primary_key_type: :uuid
end

# db/migrate/20240101000000_create_users.rb
class CreateUsers < ActiveRecord::Migration[7.1]
  def change
    create_table :users, id: :uuid do |t|
      t.string :name, null: false
      t.timestamps
    end
  end
end

1. Rails model with UUID primary key

class Order < ApplicationRecord
  # Rails 7.1+ - use :uuid as primary key type in migration
  # The model itself needs no changes - Rails handles UUID generation

  before_create :set_public_id

  private

  def set_public_id
    self.public_id ||= SecureRandom.uuid
  end
end

2. Sidekiq job ID

class ProcessOrderJob
  include Sidekiq::Job

  def perform(order_id)
    # Sidekiq assigns its own JID, but you can add a correlation ID
    correlation_id = SecureRandom.uuid
    Rails.logger.tagged(correlation_id) do
      order = Order.find(order_id)
      order.process!
    end
  end
end

3. API request tracing with Rack middleware

class RequestIdMiddleware
  def initialize(app)
    @app = app
  end

  def call(env)
    request_id = SecureRandom.uuid
    env['X-Request-ID'] = request_id
    status, headers, body = @app.call(env)
    headers['X-Request-ID'] = request_id
    [status, headers, body]
  end
end

# config/application.rb
config.middleware.use RequestIdMiddleware

How do I generate a UUID in Ruby?

SecureRandom.uuid from Ruby's standard library returns a cryptographically random v4 UUID after you require 'securerandom'. It is backed by the operating system CSPRNG. Ruby's stdlib has no v7 generator, so use a gem such as uuid7 if you need time-ordered identifiers.

Is SecureRandom.uuid cryptographically secure?

Yes. SecureRandom.uuid uses the platform CSPRNG (operating system secure random source), suitable for session tokens, API keys, and idempotency keys. Do not use non-cryptographic random sources for security-sensitive identifiers.

What is the difference between UUID v4 and v7 in Ruby?

UUID v4 (SecureRandom.uuid or equivalent) is fully random and not sortable. UUID v7 embeds a millisecond timestamp for chronological sorting (RFC 9562). Use v4 for general-purpose IDs; use v7 for database primary keys at scale.

Do I need to install a package for UUID generation in Ruby?

No additional package is required for basic v4 generation in Ruby. Check the Installation section for version-specific notes.

How do I validate a UUID string in Ruby?

Use the platform's UUID parse/validation function, or test against the RFC 4122 regex: /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i. Always validate external input at API boundaries.

Should I use UUIDs as database primary keys in Ruby applications?

UUIDs work well as primary keys for distributed systems. Prefer native UUID/BINARY(16) column types over VARCHAR(36). For very large tables, consider UUID v7 for better B-tree insert locality.

Can I generate UUIDs in Ruby without a network connection?

Yes. UUID generation uses local OS entropy sources and does not require network access. Each call is independent and thread-safe on modern platforms.

What output formats are available in Ruby?

The standard hyphenated lowercase string (36 chars) is the default. Most APIs also support 32-char hex (no hyphens) and 16-byte binary formats. Use string format for APIs and binary for database storage.

What RFC standards apply to Ruby UUID generation?

Version 4 UUIDs follow RFC 4122. UUID v7 follows RFC 9562 (May 2024). Ensure your chosen method produces compliant version and variant bits.

When should I avoid UUID v1?

Avoid UUID v1 in security-sensitive contexts - it embeds MAC address and timestamp information. Prefer v4 (SecureRandom.uuid or equivalent) unless you need legacy Cassandra timeuuid compatibility.