ActiveModel S3 Bucket Name Validator

ActiveModel validator for Amazon S3 bucket names. It implements the official AWS naming rules for:

• General purpose buckets (classic S3)
• Directory buckets (S3 Express One Zone)
• S3 Tables buckets

Works in any class using ActiveModel::Validations and in Rails/ActiveRecord models. Ships with i18n messages in multiple locales.

Add to your Gemfile:

gem "activerecord-s3-bucket-name-validator"

Then bundle:

bundle install

• Ruby: 3.1, 3.2, 3.3, 3.4 (CI runs 3.2–3.4)
• ActiveModel: 7.2, 8.0 (CI targets)
• Rails/ActiveRecord: supported via ActiveModel::Validations (no Rails runtime dependency)

Plain ActiveModel:

class StorageConfig
  include ActiveModel::Model
  attr_accessor :bucket_name
  validates :bucket_name, s3_bucket_name: true
end

ActiveRecord model:

class Storage < ApplicationRecord
  validates :bucket_name, s3_bucket_name: true
end

• type — :general_purpose (default), :directory, or :table
• transfer_acceleration — when true, periods are forbidden for general-purpose buckets

Examples:

validates :bucket_name, s3_bucket_name: { transfer_acceleration: true }
validates :bucket_name, s3_bucket_name: { type: :directory }
validates :bucket_name, s3_bucket_name: { type: :table }

Error keys provided:

• activemodel.errors.messages.s3_bucket_name_invalid_general
• activemodel.errors.messages.s3_bucket_name_invalid_transfer_acceleration
• activemodel.errors.messages.s3_bucket_name_invalid_directory
• activemodel.errors.messages.s3_bucket_name_invalid_table

Locales shipped: en, es, it, fr, de, pt-BR, ja, ko, zh-CN, zh-TW, ru, nl.

Rails loads locales via a Railtie; plain ActiveModel loads them at require-time. Override by adding your own YAML with the same keys.

• Length 3–63, allowed characters, begin/end alphanumeric
• No adjacent periods; not IP-like (general purpose)
• Reserved prefixes/suffixes per AWS docs (for example xn--, sthree-, amzn-s3-demo-, -s3alias, --ol-s3, .mrap, --x-s3, --table-s3)
• Directory buckets must end with --<zone-id>--x-s3
• S3 Tables buckets disallow periods and underscores
• Optional TA mode forbids periods

Note: Global/partition uniqueness and immutability are service-side constraints and not enforced locally.

Valid (general purpose):

my-example-bucket
example.com

Invalid (general purpose):

ex..ample
192.168.5.4
xn--abc
foo--x-s3

# ActiveModel-only
bundle install
bundle exec rake test

# With ActiveRecord integration (in-memory sqlite)
AR_INTEGRATION=1 ACTIVERECORD_VERSION="~> 8.0" bundle install
AR_INTEGRATION=1 ACTIVERECORD_VERSION="~> 8.0" bundle exec rake test

MIT — see LICENSE.txt.