diff --git a/.rubocop.yml b/.rubocop.yml
new file mode 100644
index 0000000..6e22451
--- /dev/null
+++ b/.rubocop.yml
@@ -0,0 +1,35 @@
+require:
+  - rubocop-performance
+  - rubocop-rake
+
+AllCops:
+  NewCops: enable
+  TargetRubyVersion: 3.0
+
+Metrics/MethodLength:
+  Max: 30
+
+Metrics/ClassLength:
+  Max: 200
+
+Metrics/ModuleLength:
+  Max: 200
+
+Metrics/BlockLength:
+  Max: 50
+
+Gemspec/DevelopmentDependencies:
+  EnforcedStyle: gemspec
+
+# TODO: Enable these cops after fixing the issues
+Metrics/CyclomaticComplexity:
+  Enabled: false
+
+Metrics/PerceivedComplexity:
+  Enabled: false
+
+Metrics/AbcSize:
+  Enabled: false
+
+Style/Documentation:
+  Enabled: false
diff --git a/Gemfile b/Gemfile
index fdc9cbb..bccc7f9 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 source 'https://rubygems.org'
 
 # Declare your gem's dependencies in whatever.gemspec.
diff --git a/Gemfile.lock b/Gemfile.lock
index b89805f..e4c0cd9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -57,6 +57,11 @@ GEM
       unicode-display_width (>= 2.4.0, < 3.0)
     rubocop-ast (1.31.3)
       parser (>= 3.3.1.0)
+    rubocop-performance (1.21.0)
+      rubocop (>= 1.48.1, < 2.0)
+      rubocop-ast (>= 1.31.1, < 2.0)
+    rubocop-rake (0.6.0)
+      rubocop (~> 1.0)
     ruby-progressbar (1.13.0)
     strscan (3.1.0)
     thor (0.20.3)
@@ -73,6 +78,8 @@ DEPENDENCIES
   rspec
   rspec-collection_matchers
   rubocop
+  rubocop-performance
+  rubocop-rake
 
 BUNDLED WITH
-   2.1.4
+   2.5.11
diff --git a/Rakefile b/Rakefile
index f34a48c..cffdd09 100644
--- a/Rakefile
+++ b/Rakefile
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rspec/core/rake_task'
 
 RSpec::Core::RakeTask.new(:spec)
diff --git a/html2text.gemspec b/html2text.gemspec
index 9213100..4385634 100644
--- a/html2text.gemspec
+++ b/html2text.gemspec
@@ -1,4 +1,6 @@
-$:.push File.expand_path('lib', __dir__)
+# frozen_string_literal: true
+
+$LOAD_PATH.push File.expand_path('lib', __dir__)
 
 # Maintain your gem's version:
 require 'html2text/version'
@@ -13,9 +15,9 @@ Gem::Specification.new do |s|
   s.summary     = 'Convert HTML into plain text.'
   s.description = 'A Ruby component to convert HTML into a plain text format.'
   s.license     = 'MIT'
+  s.required_ruby_version = '>= 3.0'
 
   s.files = Dir['lib/**/*', 'LICENSE.md', 'README.md', 'CHANGELOG.md']
-  s.test_files = Dir['spec/**/*']
 
   s.add_dependency 'nokogiri', ['>= 1.0', '< 2.0']
 
@@ -25,4 +27,8 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'rspec'
   s.add_development_dependency 'rspec-collection_matchers'
   s.add_development_dependency 'rubocop'
+  s.add_development_dependency 'rubocop-performance'
+  s.add_development_dependency 'rubocop-rake'
+
+  s.metadata['rubygems_mfa_required'] = 'true'
 end
diff --git a/lib/html2text.rb b/lib/html2text.rb
index 7abc7d3..a332387 100644
--- a/lib/html2text.rb
+++ b/lib/html2text.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'nokogiri'
 
 class Html2Text
@@ -10,7 +12,7 @@ def initialize(doc)
   def self.convert(html)
     html = html.to_s
 
-    if is_office_document?(html)
+    if office_document?(html)
       # Emulate the CSS rendering of Office documents
       html = html.gsub('<p class=MsoNormal>', '<br>')
                  .gsub('<o:p>&nbsp;</o:p>', '<br>')
@@ -58,15 +60,15 @@ def remove_leading_and_trailing_whitespace(text)
                 end
     end
 
-    output.join('')
+    output.join
   end
 
-  private
-
-  def self.is_office_document?(text)
+  private_class_method def self.office_document?(text)
     text.include?('urn:schemas-microsoft-com:office')
   end
 
+  private
+
   def remove_unnecessary_empty_lines(text)
     text.gsub(/\n\n\n*/im, "\n\n")
   end
@@ -99,7 +101,7 @@ def iterate_over(node)
     end
     output << suffix_whitespace(node)
 
-    output = output.compact.join('') || ''
+    output = output.compact.join || ''
 
     unless node.name.nil?
       if node.name.downcase == 'a'
@@ -112,6 +114,7 @@ def iterate_over(node)
     output
   end
 
+  # rubocop:disable Lint/DuplicateBranch
   def prefix_whitespace(node)
     case node.name.downcase
     when 'hr'
@@ -140,7 +143,9 @@ def prefix_whitespace(node)
       '- '
     end
   end
+  # rubocop:enable Lint/DuplicateBranch
 
+  # rubocop:disable Lint/DuplicateBranch
   def suffix_whitespace(node)
     case node.name.downcase
     when 'h1', 'h2', 'h3', 'h4', 'h5', 'h6'
@@ -164,6 +169,7 @@ def suffix_whitespace(node)
       end
     end
   end
+  # rubocop:enable Lint/DuplicateBranch
 
   # links are returned in [text](link) format
   def wrap_link(node, output)
@@ -208,9 +214,9 @@ def wrap_link(node, output)
 
   def image_text(node)
     if node.attribute('title')
-      '[' + node.attribute('title').to_s + ']'
+      "[#{node.attribute('title')}]"
     elsif node.attribute('alt')
-      '[' + node.attribute('alt').to_s + ']'
+      "[#{node.attribute('alt')}]"
     else
       ''
     end
@@ -224,7 +230,7 @@ def next_node_name(node)
       next_node = next_node.next_sibling
     end
 
-    return unless next_node && next_node.element?
+    return unless next_node&.element?
 
     next_node.name.downcase
   end
@@ -241,7 +247,7 @@ def previous_node_name(node)
       previous_node = previous_node.previous_sibling
     end
 
-    return unless previous_node && previous_node.element?
+    return unless previous_node&.element?
 
     previous_node.name.downcase
   end
diff --git a/lib/html2text/version.rb b/lib/html2text/version.rb
index 464f127..3a6a6a4 100644
--- a/lib/html2text/version.rb
+++ b/lib/html2text/version.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Html2Text
   VERSION = '0.3.1'
 end
diff --git a/spec/examples_spec.rb b/spec/examples_spec.rb
index c0e0010..0330eeb 100644
--- a/spec/examples_spec.rb
+++ b/spec/examples_spec.rb
@@ -1,13 +1,15 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe Html2Text do
   describe '#convert' do
     let(:text) { Html2Text.convert(html) }
 
-    examples = Dir[File.dirname(__FILE__) + '/examples/*.html']
+    examples = Dir["#{File.dirname(__FILE__)}/examples/*.html"]
 
     examples.each do |filename|
-      context "#{filename}" do
+      context filename.to_s do
         let(:html) { File.read(filename) }
         let(:text_file) { filename.sub('.html', '.txt') }
         let(:expected) { Html2Text.fix_newlines(File.read(text_file)) }
@@ -18,11 +20,7 @@
 
         it 'converts to text' do
           # Write the output if it failed, for easier comparison
-          unless text.eql?(expected)
-            File.open(filename.sub('.html', '.output'), 'w') do |fp|
-              fp.write(text)
-            end
-          end
+          File.write(filename.sub('.html', '.output'), text) unless text.eql?(expected)
 
           # Quick check, don't try to generate a 500kb+ diff,
           # which can halt the rspec for minutes+
diff --git a/spec/html2text_spec.rb b/spec/html2text_spec.rb
index 1d28b25..516d64d 100644
--- a/spec/html2text_spec.rb
+++ b/spec/html2text_spec.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'spec_helper'
 
 describe Html2Text do
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index a7cdbb6..e2acb5a 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 require 'rspec'
 require 'rspec/collection_matchers'