diff --git a/.rubocop.yml b/.rubocop.yml
index e04cbea..7cb7e9c 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -64,3 +64,7 @@ Style/NegatedIfElseCondition:
 Style/NumericLiterals:
   Exclude:
     - spec/dummy/db/**/schema*.rb
+
+Style/StringLiterals:
+  Enabled: true
+  EnforcedStyle: double_quotes
diff --git a/Gemfile b/Gemfile
index 8f70f1f..bca1a44 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,72 +1,72 @@
 # frozen_string_literal: true
 
-source 'https://rubygems.org'
+source "https://rubygems.org"
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-if ENV['DEVEL'] == '1'
-  gem 'active_storage_db', path: './'
+if ENV["DEVEL"] == "1"
+  gem "active_storage_db", path: "./"
 else
   gemspec
 end
 
-ruby_ver = ENV.fetch('RUBY_VERSION', '')
-rails_ver = ENV.fetch('RAILS_VERSION', '')
+ruby_ver = ENV.fetch("RUBY_VERSION", "")
+rails_ver = ENV.fetch("RAILS_VERSION", "")
 
 rails =
   if rails_ver.empty?
-    ['rails']
-  elsif rails_ver.count('.') < 2
-    ['rails', "~> #{rails_ver}"]
+    ["rails"]
+  elsif rails_ver.count(".") < 2
+    ["rails", "~> #{rails_ver}"]
   else
-    ['rails', rails_ver]
+    ["rails", rails_ver]
   end
 gem(*rails)
 
-ruby32 = ruby_ver.empty? || Gem::Version.new(ruby_ver) >= Gem::Version.new('3.2')
-gem 'zeitwerk', '~> 2.6.18' unless ruby32
+ruby32 = ruby_ver.empty? || Gem::Version.new(ruby_ver) >= Gem::Version.new("3.2")
+gem "zeitwerk", "~> 2.6.18" unless ruby32
 
 # DB driver
-case ENV.fetch('DB_TEST', nil)
-when 'mssql'
-  gem 'activerecord-sqlserver-adapter'
-  gem 'tiny_tds'
-when 'mysql'
-  gem 'mysql2'
-when 'postgres'
-  gem 'pg'
+case ENV.fetch("DB_TEST", nil)
+when "mssql"
+  gem "activerecord-sqlserver-adapter"
+  gem "tiny_tds"
+when "mysql"
+  gem "mysql2"
+when "postgres"
+  gem "pg"
 else
-  rails72 = rails_ver.empty? || Gem::Version.new(rails_ver) >= Gem::Version.new('7.2')
-  sqlite3 = ruby32 && rails72 ? ['sqlite3'] : ['sqlite3', '~> 1.4']
+  rails72 = rails_ver.empty? || Gem::Version.new(rails_ver) >= Gem::Version.new("7.2")
+  sqlite3 = ruby32 && rails72 ? ["sqlite3"] : ["sqlite3", "~> 1.4"]
   gem(*sqlite3)
 end
 
 # NOTE: to avoid error: uninitialized constant ActiveSupport::LoggerThreadSafeLevel::Logger
-gem 'concurrent-ruby', '1.3.4'
+gem "concurrent-ruby", "1.3.4"
 
-gem 'bigdecimal'
-gem 'bullet'
-gem 'image_processing', '>= 1.2'
-gem 'mutex_m'
-gem 'puma'
-gem 'sprockets-rails'
+gem "bigdecimal"
+gem "bullet"
+gem "image_processing", ">= 1.2"
+gem "mutex_m"
+gem "puma"
+gem "sprockets-rails"
 
 # Testing
-gem 'capybara'
-gem 'factory_bot_rails'
-gem 'rspec_junit_formatter'
-gem 'rspec-rails'
-gem 'selenium-webdriver'
-gem 'simplecov'
-gem 'simplecov-lcov'
+gem "capybara"
+gem "factory_bot_rails"
+gem "rspec_junit_formatter"
+gem "rspec-rails"
+gem "selenium-webdriver"
+gem "simplecov"
+gem "simplecov-lcov"
 
 # Linters
-gem 'brakeman'
-gem 'fasterer'
-gem 'rubocop'
-gem 'rubocop-packaging'
-gem 'rubocop-performance'
-gem 'rubocop-rails'
-gem 'rubocop-rspec'
+gem "brakeman"
+gem "fasterer"
+gem "rubocop"
+gem "rubocop-packaging"
+gem "rubocop-performance"
+gem "rubocop-rails"
+gem "rubocop-rspec"
 
 # Tools
-gem 'pry-rails'
+gem "pry-rails"
diff --git a/Rakefile b/Rakefile
index fd4a6cd..7175300 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,37 +1,37 @@
 # frozen_string_literal: true
 
 begin
-  require 'bundler/setup'
+  require "bundler/setup"
 rescue LoadError
-  puts 'You must `gem install bundler` and `bundle install` to run rake tasks'
+  puts "You must `gem install bundler` and `bundle install` to run rake tasks"
 end
 
-require 'rdoc/task'
+require "rdoc/task"
 
 RDoc::Task.new(:rdoc) do |rdoc|
-  rdoc.rdoc_dir = 'rdoc'
-  rdoc.title    = 'ActiveStorageDB'
-  rdoc.options << '--line-numbers'
-  rdoc.rdoc_files.include('README.md')
-  rdoc.rdoc_files.include('lib/**/*.rb')
+  rdoc.rdoc_dir = "rdoc"
+  rdoc.title    = "ActiveStorageDB"
+  rdoc.options << "--line-numbers"
+  rdoc.rdoc_files.include("README.md")
+  rdoc.rdoc_files.include("lib/**/*.rb")
 end
 
 APP_RAKEFILE = File.expand_path("spec/dummy/Rakefile", __dir__)
-load 'rails/tasks/engine.rake'
+load "rails/tasks/engine.rake"
 
-load 'rails/tasks/statistics.rake'
+load "rails/tasks/statistics.rake"
 
-require 'bundler/gem_tasks'
+require "bundler/gem_tasks"
 
 begin
-  require 'rspec/core/rake_task'
+  require "rspec/core/rake_task"
 
   RSpec::Core::RakeTask.new(:spec) do |t|
     # t.ruby_opts = %w[-w]
-    t.rspec_opts = ['--color', '--format documentation']
+    t.rspec_opts = ["--color", "--format documentation"]
   end
 
   task default: :spec
 rescue LoadError
-  puts '! LoadError: no RSpec available'
+  puts "! LoadError: no RSpec available"
 end
diff --git a/config/initializers/inflections.rb b/config/initializers/inflections.rb
index 31b2ad4..c4331ae 100644
--- a/config/initializers/inflections.rb
+++ b/config/initializers/inflections.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 ActiveSupport::Inflector.inflections(:en) do |inflect|
-  inflect.acronym 'DB'
+  inflect.acronym "DB"
 end
diff --git a/config/routes.rb b/config/routes.rb
index 7eadd86..bd97597 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
 ActiveStorageDB::Engine.routes.draw do
-  get '/files/:encoded_key/*filename', to: 'files#show', as: :service
-  put '/files/:encoded_token', to: 'files#update', as: :update_service
+  get "/files/:encoded_key/*filename", to: "files#show", as: :service
+  put "/files/:encoded_token", to: "files#update", as: :update_service
 end
diff --git a/lib/active_storage_db.rb b/lib/active_storage_db.rb
index 734ee1a..bd331f9 100644
--- a/lib/active_storage_db.rb
+++ b/lib/active_storage_db.rb
@@ -1,7 +1,7 @@
 # frozen_string_literal: true
 
-require 'active_storage_db/engine'
-require 'active_storage/service/db_service'
+require "active_storage_db/engine"
+require "active_storage/service/db_service"
 
 module ActiveStorageDB
 end
diff --git a/lib/active_storage_db/version.rb b/lib/active_storage_db/version.rb
index 2bea9d5..6c9de13 100644
--- a/lib/active_storage_db/version.rb
+++ b/lib/active_storage_db/version.rb
@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
 module ActiveStorageDB
-  VERSION = '1.6.0'
+  VERSION = "1.6.0"
 end
diff --git a/spec/dummy/config/application.rb b/spec/dummy/config/application.rb
index ca4c755..4c9c6c7 100644
--- a/spec/dummy/config/application.rb
+++ b/spec/dummy/config/application.rb
@@ -24,7 +24,7 @@ class Application < Rails::Application
     # config.time_zone = "Central Time (US & Canada)"
     # config.eager_load_paths << Rails.root.join("extras")
 
-    config.hosts << 'test.example.com'
+    config.hosts << "test.example.com"
 
     config.before_initialize do
       FactoryBot.definition_file_paths << Rails.root.join("../factories") if defined?(FactoryBot)
diff --git a/spec/dummy/config/routes.rb b/spec/dummy/config/routes.rb
index ac58b05..b0c5cd6 100644
--- a/spec/dummy/config/routes.rb
+++ b/spec/dummy/config/routes.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
 Rails.application.routes.draw do
-  mount ActiveStorageDB::Engine => '/active_storage_db'
+  mount ActiveStorageDB::Engine => "/active_storage_db"
 
   resources :posts
 
-  root 'posts#index'
+  root "posts#index"
 end
diff --git a/spec/factories/active_storage_db_files.rb b/spec/factories/active_storage_db_files.rb
index 00e5b31..c228138 100644
--- a/spec/factories/active_storage_db_files.rb
+++ b/spec/factories/active_storage_db_files.rb
@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
 FactoryBot.define do
-  factory :active_storage_db_file, class: 'ActiveStorageDB::File' do
-    ref { ('a'..'z').to_a.sample(32).join }
+  factory :active_storage_db_file, class: "ActiveStorageDB::File" do
+    ref { ("a".."z").to_a.sample(32).join }
 
     data do
       (+"\211PNG\r\n\032\n\000\000\000\rIHDR\000\000\000\020\000\000\000\020\001\003\000\000\000%=m\"\000\000\000\006PLTE\000\000\000\377\377\377\245\331\237\335\000\000\0003IDATx\234c\370\377\237\341\377_\206\377\237\031\016\2603\334?\314p\1772\303\315\315\f7\215\031\356\024\203\320\275\317\f\367\201R\314\f\017\300\350\377\177\000Q\206\027(\316]\233P\000\000\000\000IEND\256B`\202").force_encoding(Encoding::BINARY)
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index 39c80df..f1ccee0 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -1,9 +1,9 @@
 # frozen_string_literal: true
 
-ENV['RAILS_ENV'] = 'test'
+ENV["RAILS_ENV"] = "test"
 
-require 'simplecov'
-require 'simplecov-lcov'
+require "simplecov"
+require "simplecov-lcov"
 
 SimpleCov::Formatter::LcovFormatter.config do |c|
   c.report_with_single_file = true
@@ -26,15 +26,15 @@
   add_filter %r{^/vendor/}
 end
 
-require 'spec_helper'
+require "spec_helper"
 
 require File.expand_path("dummy/config/environment.rb", __dir__)
 
-abort('The Rails environment is running in production mode!') if Rails.env.production?
-require 'rspec/rails'
-require 'factory_bot_rails'
+abort("The Rails environment is running in production mode!") if Rails.env.production?
+require "rspec/rails"
+require "factory_bot_rails"
 
-support_files = File.expand_path('support/**/*.rb', __dir__)
+support_files = File.expand_path("support/**/*.rb", __dir__)
 Dir[support_files].sort.each { |f| require f }
 
 RSpec.configure do |config|
@@ -50,14 +50,14 @@
         ActiveRecord::Base.connection_config
       end
 
-    intro = ('-' * 80)
+    intro = ("-" * 80)
     intro << "\n"
     intro << "- Ruby:          #{RUBY_VERSION}\n"
     intro << "- Rails:         #{Rails.version}\n"
     intro << "- ActiveStorage: #{ActiveStorage.version}\n"
     intro << "- DB adapter:    #{db_config[:adapter]}\n"
     intro << "- DB name:       #{db_config[:database]}\n"
-    intro << ('-' * 80)
+    intro << ("-" * 80)
 
     RSpec.configuration.reporter.message(intro)
   end
diff --git a/spec/requests/file_url_spec.rb b/spec/requests/file_url_spec.rb
index dd7d392..065a5d1 100644
--- a/spec/requests/file_url_spec.rb
+++ b/spec/requests/file_url_spec.rb
@@ -1,10 +1,10 @@
 # frozen_string_literal: true
 
-RSpec.describe 'File URL' do
+RSpec.describe "File URL" do
   let(:app_url_helpers) { Rails.application.routes.url_helpers }
   let(:engine_url_helpers) { ActiveStorageDB::Engine.routes.url_helpers }
 
-  it 'has the service URL in the engine URL helpers' do
+  it "has the service URL in the engine URL helpers" do
     expect(app_url_helpers).to respond_to :active_storage_db_path
     expect(engine_url_helpers).to respond_to :service_url
   end