diff --git a/Changelog.md b/Changelog.md
index da6944a2d..fa3bcda4c 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,3 +1,10 @@
+# v0.10.33 2021-08-25
+
+* [#1249](https://github.com/mbj/mutant/pull/1249/files)
+  Add `mutant util mutation` subcommand to allow inspect mutations of
+  a code snippet outside a booted environment.
+  This eases debugging, learning and mutant developers life.
+
 # v0.10.32 2021-05-16
 
 * [#1235](https://github.com/mbj/mutant/pull/1235)
diff --git a/lib/mutant.rb b/lib/mutant.rb
index 3380a9f15..c2590a573 100644
--- a/lib/mutant.rb
+++ b/lib/mutant.rb
@@ -197,6 +197,7 @@ module Mutant
 require 'mutant/cli/command/environment/show'
 require 'mutant/cli/command/environment/subject'
 require 'mutant/cli/command/environment/test'
+require 'mutant/cli/command/util'
 require 'mutant/cli/command/root'
 require 'mutant/runner'
 require 'mutant/runner/sink'
@@ -212,6 +213,7 @@ module Mutant
 require 'mutant/reporter/cli/printer/env_progress'
 require 'mutant/reporter/cli/printer/env_result'
 require 'mutant/reporter/cli/printer/isolation_result'
+require 'mutant/reporter/cli/printer/mutation'
 require 'mutant/reporter/cli/printer/mutation_result'
 require 'mutant/reporter/cli/printer/status_progressive'
 require 'mutant/reporter/cli/printer/subject_result'
diff --git a/lib/mutant/cli/command.rb b/lib/mutant/cli/command.rb
index 5afde7a5d..0a19853c4 100644
--- a/lib/mutant/cli/command.rb
+++ b/lib/mutant/cli/command.rb
@@ -69,6 +69,8 @@ def zombie?
         false
       end
 
+      abstract_method :action
+
     private
 
       def subcommands
diff --git a/lib/mutant/cli/command/root.rb b/lib/mutant/cli/command/root.rb
index 949ebf2ff..2d862551a 100644
--- a/lib/mutant/cli/command/root.rb
+++ b/lib/mutant/cli/command/root.rb
@@ -10,7 +10,7 @@ class Environment < self
       class Root < self
         NAME              = 'mutant'
         SHORT_DESCRIPTION = 'mutation testing engine main command'
-        SUBCOMMANDS       = [Environment::Run, Environment, Subscription].freeze
+        SUBCOMMANDS       = [Environment::Run, Environment, Subscription, Util].freeze
       end # Root
     end # Command
   end # CLI
diff --git a/lib/mutant/cli/command/util.rb b/lib/mutant/cli/command/util.rb
new file mode 100644
index 000000000..27cd36c5a
--- /dev/null
+++ b/lib/mutant/cli/command/util.rb
@@ -0,0 +1,100 @@
+# frozen_string_literal: true
+
+module Mutant
+  module CLI
+    class Command
+      class Util < self
+        NAME              = 'util'
+        SHORT_DESCRIPTION = 'Utility subcommands'
+
+        class Mutation < self
+          NAME              = 'mutation'
+          SHORT_DESCRIPTION = 'Print mutations of a code snippet'
+          SUBCOMMANDS       = [].freeze
+          OPTIONS           = %i[add_target_options].freeze
+
+          def action
+            @targets.each(&method(:print_mutations))
+            Either::Right.new(nil)
+          end
+
+        private
+
+          class Target
+            include Adamantium
+
+            def node
+              Unparser.parse(source)
+            end
+            memoize :node
+
+            class File < self
+              include Concord.new(:pathname, :source)
+
+              public :source
+
+              def identification
+                "file:#{pathname}"
+              end
+            end # File
+
+            class Source < self
+              include Concord::Public.new(:source)
+
+              def identification
+                '<cli-source>'
+              end
+            end # source
+          end # Target
+
+          def initialize(_arguments)
+            super
+
+            @targets = []
+          end
+
+          def add_target_options(parser)
+            parser.on('-e', '--evaluate SOURCE') do |source|
+              @targets << Target::Source.new(source)
+            end
+          end
+
+          def print_mutations(target)
+            world.stdout.puts(target.identification)
+            Mutator.mutate(target.node).each do |mutation|
+              Reporter::CLI::Printer::Mutation.call(
+                world.stdout,
+                Mutant::Mutation::Evil.new(target, mutation)
+              )
+            end
+          end
+
+          def parse_remaining_arguments(arguments)
+            @targets.concat(
+              arguments.map do |argument|
+                parse_pathname(argument)
+                  .bind(&method(:read_file))
+                  .from_right { |error| return Either::Left.new(error) }
+              end
+            )
+
+            Either::Right.new(self)
+          end
+
+          def read_file(pathname)
+            Either::Right.new(Target::File.new(pathname, pathname.read))
+          rescue StandardError => exception
+            Either::Left.new("Cannot read file: #{exception}")
+          end
+
+          def parse_pathname(input)
+            Either.wrap_error(ArgumentError) { Pathname.new(input) }
+              .lmap(&:message)
+          end
+        end # Mutation
+
+        SUBCOMMANDS = [Mutation].freeze
+      end # Util
+    end # Command
+  end # CLI
+end # Mutant
diff --git a/lib/mutant/mutation.rb b/lib/mutant/mutation.rb
index 33c1f2777..0c6f8fda2 100644
--- a/lib/mutant/mutation.rb
+++ b/lib/mutant/mutation.rb
@@ -72,6 +72,15 @@ def insert(kernel)
       )
     end
 
+    # Rendered mutation diff
+    #
+    # @return [String, nil]
+    #   the diff, if present
+    def diff
+      Unparser::Diff.build(original_source, source)
+    end
+    memoize :diff
+
   private
 
     def sha1
@@ -80,7 +89,6 @@ def sha1
 
     # Evil mutation that should case mutations to fail tests
     class Evil < self
-
       SYMBOL            = 'evil'
       TEST_PASS_SUCCESS = false
 
diff --git a/lib/mutant/reporter/cli/printer/mutation.rb b/lib/mutant/reporter/cli/printer/mutation.rb
new file mode 100644
index 000000000..1cb447065
--- /dev/null
+++ b/lib/mutant/reporter/cli/printer/mutation.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module Mutant
+  class Reporter
+    class CLI
+      class Printer
+        # Reporter for mutations
+        class Mutation < self
+          NO_DIFF_MESSAGE = <<~'MESSAGE'
+            --- Internal failure ---
+            BUG: A generted mutation did not result in exactly one diff hunk!
+            This is an invariant violation by the mutation generation engine.
+            Please report a reproduction to https://github.com/mbj/mutant
+            Original unparsed source:
+            %s
+            Original AST:
+            %s
+            Mutated unparsed source:
+            %s
+            Mutated AST:
+            %s
+          MESSAGE
+
+          SEPARATOR = '-----------------------'
+
+          # Run report printer
+          #
+          # @return [undefined]
+          def run
+            diff = object.diff
+            diff = color? ? diff.colorized_diff : diff.diff
+
+            if diff
+              output.write(diff)
+            else
+              print_no_diff_message
+            end
+          end
+
+          def print_no_diff_message
+            info(
+              NO_DIFF_MESSAGE,
+              object.original_source,
+              original_node.inspect,
+              object.source,
+              object.node.inspect
+            )
+          end
+
+          def original_node
+            object.subject.node
+          end
+
+        end # MutationResult
+      end # Printer
+    end # CLI
+  end # Reporter
+end # Mutant
diff --git a/lib/mutant/reporter/cli/printer/mutation_result.rb b/lib/mutant/reporter/cli/printer/mutation_result.rb
index 5561d3701..8af68212b 100644
--- a/lib/mutant/reporter/cli/printer/mutation_result.rb
+++ b/lib/mutant/reporter/cli/printer/mutation_result.rb
@@ -66,23 +66,7 @@ def print_details
           end
 
           def evil_details
-            diff = Unparser::Diff.build(mutation.original_source, mutation.source)
-            diff = color? ? diff.colorized_diff : diff.diff
-            if diff
-              output.write(diff)
-            else
-              print_no_diff_message
-            end
-          end
-
-          def print_no_diff_message
-            info(
-              NO_DIFF_MESSAGE,
-              mutation.original_source,
-              original_node.inspect,
-              mutation.source,
-              mutation.node.inspect
-            )
+            visit(Mutation, mutation)
           end
 
           def noop_details
@@ -90,11 +74,7 @@ def noop_details
           end
 
           def neutral_details
-            info(NEUTRAL_MESSAGE, original_node.inspect, mutation.source)
-          end
-
-          def original_node
-            mutation.subject.node
+            info(NEUTRAL_MESSAGE, mutation.node.inspect, mutation.source)
           end
 
         end # MutationResult
diff --git a/spec/unit/mutant/cli_spec.rb b/spec/unit/mutant/cli_spec.rb
index 61fcad23c..5d5ca2a70 100644
--- a/spec/unit/mutant/cli_spec.rb
+++ b/spec/unit/mutant/cli_spec.rb
@@ -2,13 +2,13 @@
 
 RSpec.describe Mutant::CLI do
   describe '.parse' do
-    let(:env_config)    { Mutant::Config::DEFAULT.with(jobs: 4) }
-    let(:events)        { []                                    }
-    let(:expect_zombie) { false                                 }
-    let(:kernel)        { class_double(Kernel)                  }
-    let(:stderr)        { instance_double(IO, :stderr)          }
-    let(:stdout)        { instance_double(IO, :stdout)          }
-    let(:timer)         { instance_double(Mutant::Timer)        }
+    let(:env_config)    { Mutant::Config::DEFAULT.with(jobs: 4)     }
+    let(:events)        { []                                        }
+    let(:expect_zombie) { false                                     }
+    let(:kernel)        { class_double(Kernel)                      }
+    let(:stderr)        { instance_double(IO, :stderr, tty?: false) }
+    let(:stdout)        { instance_double(IO, :stdout, tty?: false) }
+    let(:timer)         { instance_double(Mutant::Timer)            }
 
     let(:world) do
       instance_double(
@@ -31,9 +31,15 @@ def apply
       allow(stderr)
         .to receive(:puts) { |message| events << [:stderr, :puts, message] }
 
+      allow(stderr)
+        .to receive(:write) { |message| events << [:stderr, :write, message] }
+
       allow(stdout)
         .to receive(:puts) { |message| events << [:stdout, :puts, message] }
 
+      allow(stdout)
+        .to receive(:write) { |message| events << [:stdout, :write, message] }
+
       allow(Mutant::Config).to receive_messages(env: env_config)
     end
 
@@ -79,7 +85,7 @@ def self.make
 
     def self.main_body
       <<~'MESSAGE'.strip
-        usage: mutant <run|environment|subscription> [options]
+        usage: mutant <run|environment|subscription|util> [options]
 
         Summary: mutation testing engine main command
 
@@ -93,6 +99,7 @@ def self.main_body
         run          - Run code analysis
         environment  - Environment subcommands
         subscription - Subscription subcommands
+        util         - Utility subcommands
       MESSAGE
     end
 
@@ -261,6 +268,110 @@ def self.main_body
       }
     end
 
+    make do
+      message = <<~'MESSAGE'
+        usage: mutant util <mutation> [options]
+
+        Summary: Utility subcommands
+
+        Global Options:
+
+                --help                       Print help
+                --version                    Print mutants version
+
+        Available subcommands:
+
+        mutation - Print mutations of a code snippet
+      MESSAGE
+
+      {
+        arguments:       %w[util --help],
+        expected_events: [[:stdout, :puts, message]],
+        expected_exit:   true,
+        expected_zombie: false
+      }
+    end
+
+    make do
+      message = <<~'MESSAGE'
+        usage: mutant util mutation [options]
+
+        Summary: Print mutations of a code snippet
+
+        Global Options:
+
+                --help                       Print help
+                --version                    Print mutants version
+
+
+            -e, --evaluate SOURCE
+      MESSAGE
+
+      {
+        arguments:       %w[util mutation --help],
+        expected_events: [[:stdout, :puts, message]],
+        expected_exit:   true,
+        expected_zombie: false
+      }
+    end
+
+    make do
+      message = <<~'MESSAGE'
+        @@ -1 +1 @@
+        -true
+        +false
+      MESSAGE
+
+      {
+        arguments:       %w[util mutation -e true],
+        expected_events: [
+          [:stdout, :puts, '<cli-source>'],
+          [:stdout, :write, message]
+        ],
+        expected_exit:   true,
+        expected_zombie: false
+      }
+    end
+
+    make do
+      message = <<~'MESSAGE'
+        @@ -1 +1 @@
+        -true
+        +false
+      MESSAGE
+
+      {
+        arguments:       %w[util mutation test_app/simple.rb],
+        expected_events: [
+          [:stdout, :puts, 'file:test_app/simple.rb'],
+          [:stdout, :write, message]
+        ],
+        expected_exit:   true,
+        expected_zombie: false
+      }
+    end
+
+    make do
+      {
+        arguments:       %w[util mutation] + ["\0"],
+        expected_events: [
+          [:stderr, :puts, 'pathname contains null byte']
+        ],
+        expected_exit:   false,
+        expected_zombie: false
+      }
+    end
+
+    make do
+      {
+        arguments:       %w[util mutation does-not-exist.rb],
+        expected_events: [[:stderr, :puts,
+                           'Cannot read file: No such file or directory @ rb_sysopen - does-not-exist.rb']],
+        expected_exit:   false,
+        expected_zombie: false
+      }
+    end
+
     @tests.each do |example|
       context example.arguments.inspect do
         example.to_h.each do |key, value|
diff --git a/spec/unit/mutant/mutation_spec.rb b/spec/unit/mutant/mutation_spec.rb
index 35cd7a241..aa043dbdc 100644
--- a/spec/unit/mutant/mutation_spec.rb
+++ b/spec/unit/mutant/mutation_spec.rb
@@ -144,6 +144,18 @@ def apply
     end
   end
 
+  describe '#diff' do
+    def apply
+      object.diff
+    end
+
+    it 'returns expected diff' do
+      expect(apply).to eql(
+        Unparser::Diff.new(%w[original], %w[nil])
+      )
+    end
+  end
+
   describe '#identification' do
 
     subject { object.identification }
diff --git a/test_app/simple.rb b/test_app/simple.rb
new file mode 100644
index 000000000..27ba77dda
--- /dev/null
+++ b/test_app/simple.rb
@@ -0,0 +1 @@
+true