diff --git a/lib/nanoc/base/checksummer.rb b/lib/nanoc/base/checksummer.rb
index df270160ae..0a5f009789 100644
--- a/lib/nanoc/base/checksummer.rb
+++ b/lib/nanoc/base/checksummer.rb
@@ -5,6 +5,8 @@ module Nanoc
   #
   # A checksum is a string, such as “mL+TaqNsEeiPkWloPgCtAofT1yg=”, that is used
   # to determine whether a piece of data has changed.
+  #
+  # @api private
   class Checksummer
     class << self
       # @param obj The object to create a checksum for
diff --git a/lib/nanoc/base/compilation/compiler.rb b/lib/nanoc/base/compilation/compiler.rb
index 4b0e7502d7..222d0ccf50 100644
--- a/lib/nanoc/base/compilation/compiler.rb
+++ b/lib/nanoc/base/compilation/compiler.rb
@@ -37,6 +37,8 @@ module Nanoc
   #
   # * `processing_ended` — indicates that the compiler has finished processing
   #   the specified object.
+  #
+  # @api private
   class Compiler
     extend Nanoc::Memoization
 
diff --git a/lib/nanoc/base/compilation/outdatedness_reasons.rb b/lib/nanoc/base/compilation/outdatedness_reasons.rb
index a4683a190c..b9b8b9f61e 100644
--- a/lib/nanoc/base/compilation/outdatedness_reasons.rb
+++ b/lib/nanoc/base/compilation/outdatedness_reasons.rb
@@ -2,6 +2,8 @@
 
 module Nanoc
   # Module that contains all outdatedness reasons.
+  #
+  # @api private
   module OutdatednessReasons
     # A generic outdatedness reason. An outdatedness reason is basically a
     # descriptive message that explains why a given object is outdated.
diff --git a/lib/nanoc/base/compilation/rule.rb b/lib/nanoc/base/compilation/rule.rb
index d66332260e..14bfe95beb 100644
--- a/lib/nanoc/base/compilation/rule.rb
+++ b/lib/nanoc/base/compilation/rule.rb
@@ -2,6 +2,8 @@
 
 module Nanoc
   # Contains the processing information for a item.
+  #
+  # @api private
   class Rule
     # @return [Regexp] The regex that determines which items this rule can be
     #   applied to. This rule can be applied to items with a identifier
diff --git a/lib/nanoc/base/directed_graph.rb b/lib/nanoc/base/directed_graph.rb
index af6685ef93..04cb439b89 100644
--- a/lib/nanoc/base/directed_graph.rb
+++ b/lib/nanoc/base/directed_graph.rb
@@ -28,6 +28,8 @@ module Nanoc
   #     # => %w( c )
   #   graph.predecessors_of('d').sort
   #     # => %w( b c )
+  #
+  # @api private
   class DirectedGraph
     # @group Creating a graph
 
diff --git a/lib/nanoc/base/errors.rb b/lib/nanoc/base/errors.rb
index 221288076d..369e8bb1a1 100644
--- a/lib/nanoc/base/errors.rb
+++ b/lib/nanoc/base/errors.rb
@@ -2,6 +2,8 @@
 
 module Nanoc
   # Module that contains all nanoc-specific errors.
+  #
+  # @api private
   module Errors
     # Generic error. Superclass for all nanoc-specific errors.
     class Generic < ::StandardError
diff --git a/lib/nanoc/base/memoization.rb b/lib/nanoc/base/memoization.rb
index 6d0040cd91..3b41996f6a 100644
--- a/lib/nanoc/base/memoization.rb
+++ b/lib/nanoc/base/memoization.rb
@@ -3,6 +3,8 @@
 module Nanoc
   # Adds support for memoizing functions.
   #
+  # @api private
+  #
   # @since 3.2.0
   module Memoization
     # Memoizes the method with the given name. The modified method will cache
diff --git a/lib/nanoc/base/notification_center.rb b/lib/nanoc/base/notification_center.rb
index 843acdafba..deed208a33 100644
--- a/lib/nanoc/base/notification_center.rb
+++ b/lib/nanoc/base/notification_center.rb
@@ -8,6 +8,8 @@ module Nanoc
   # It is a slightly different implementation of the Observer pattern; the
   # table of subscribers is not stored in the observable object itself, but in
   # the notification center.
+  #
+  # @api private
   class NotificationCenter
     class << self
       # Adds the given block to the list of blocks that should be called when
diff --git a/lib/nanoc/base/plugin_registry.rb b/lib/nanoc/base/plugin_registry.rb
index b0cb77d7bb..f02c3247a7 100644
--- a/lib/nanoc/base/plugin_registry.rb
+++ b/lib/nanoc/base/plugin_registry.rb
@@ -4,6 +4,8 @@ module Nanoc
   # The class responsible for keeping track of all loaded plugins, such as
   # filters ({Nanoc::Filter}), data sources ({Nanoc::DataSource}) and VCSes
   # ({Nanoc::Extra::VCS}).
+  #
+  # @api private
   class PluginRegistry
     extend Nanoc::Memoization
 
diff --git a/lib/nanoc/base/source_data/code_snippet.rb b/lib/nanoc/base/source_data/code_snippet.rb
index 8b660701c7..8e3b09868f 100644
--- a/lib/nanoc/base/source_data/code_snippet.rb
+++ b/lib/nanoc/base/source_data/code_snippet.rb
@@ -2,6 +2,8 @@
 
 module Nanoc
   # Nanoc::CodeSnippet represent a piece of custom code of a nanoc site.
+  #
+  # @api private
   class CodeSnippet
     # A string containing the actual code in this code snippet.
     #
diff --git a/lib/nanoc/base/temp_filename_factory.rb b/lib/nanoc/base/temp_filename_factory.rb
index 89953ef173..c3ea43c3e7 100644
--- a/lib/nanoc/base/temp_filename_factory.rb
+++ b/lib/nanoc/base/temp_filename_factory.rb
@@ -3,6 +3,7 @@
 require 'tmpdir'
 
 module Nanoc
+  # @api private
   class TempFilenameFactory
     # @return [String] The root directory for all temporary filenames
     attr_reader :root_dir
diff --git a/lib/nanoc/cli/ansi_string_colorizer.rb b/lib/nanoc/cli/ansi_string_colorizer.rb
index d604a06e91..67062ea2a4 100644
--- a/lib/nanoc/cli/ansi_string_colorizer.rb
+++ b/lib/nanoc/cli/ansi_string_colorizer.rb
@@ -3,6 +3,8 @@
 module Nanoc::CLI
   # A simple ANSI colorizer for strings. When given a string and a list of
   # attributes, it returns a colorized string.
+  #
+  # @api private
   module ANSIStringColorizer
     # TODO: complete mapping
     MAPPING = {
diff --git a/lib/nanoc/cli/cleaning_stream.rb b/lib/nanoc/cli/cleaning_stream.rb
index 0c581eec45..6f2e1dd523 100644
--- a/lib/nanoc/cli/cleaning_stream.rb
+++ b/lib/nanoc/cli/cleaning_stream.rb
@@ -3,6 +3,8 @@
 module Nanoc::CLI
   # An output stream that passes output through stream cleaners. This can be
   # used to strip ANSI color sequences, for instance.
+  #
+  # @api private
   class CleaningStream
     # @param [IO, StringIO] stream The stream to wrap
     def initialize(stream)
diff --git a/lib/nanoc/cli/command_runner.rb b/lib/nanoc/cli/command_runner.rb
index 533bf43f42..dfce4e4edf 100644
--- a/lib/nanoc/cli/command_runner.rb
+++ b/lib/nanoc/cli/command_runner.rb
@@ -3,6 +3,8 @@
 module Nanoc::CLI
   # A command runner subclass for nanoc commands that adds nanoc-specific
   # convenience methods and error handling.
+  #
+  # @api private
   class CommandRunner < ::Cri::CommandRunner
     # @see http://rubydoc.info/gems/cri/Cri/CommandRunner#call-instance_method
     #
diff --git a/lib/nanoc/cli/logger.rb b/lib/nanoc/cli/logger.rb
index c2b7355dc0..0255c59e88 100644
--- a/lib/nanoc/cli/logger.rb
+++ b/lib/nanoc/cli/logger.rb
@@ -5,6 +5,8 @@
 module Nanoc::CLI
   # Nanoc::CLI::Logger is a singleton class responsible for generating
   # feedback in the terminal.
+  #
+  # @api private
   class Logger
     # Maps actions (`:create`, `:update`, `:identical`, `:skip` and `:delete`)
     # onto their ANSI color codes.
diff --git a/lib/nanoc/cli/stream_cleaners.rb b/lib/nanoc/cli/stream_cleaners.rb
index 532410b04d..a6a4fed06b 100644
--- a/lib/nanoc/cli/stream_cleaners.rb
+++ b/lib/nanoc/cli/stream_cleaners.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::CLI
+  # @api private
   module StreamCleaners
     autoload 'Abstract',   'nanoc/cli/stream_cleaners/abstract'
     autoload 'ANSIColors', 'nanoc/cli/stream_cleaners/ansi_colors'
diff --git a/lib/nanoc/cli/stream_cleaners/abstract.rb b/lib/nanoc/cli/stream_cleaners/abstract.rb
index 37e4dca74d..2f3e4f64a7 100644
--- a/lib/nanoc/cli/stream_cleaners/abstract.rb
+++ b/lib/nanoc/cli/stream_cleaners/abstract.rb
@@ -6,6 +6,8 @@ module Nanoc::CLI::StreamCleaners
   # can have state, so they can act as a FSM.
   #
   # @abstract Subclasses must implement {#clean}
+  #
+  # @api private
   class Abstract
     # Returns a cleaned version of the given string.
     #
diff --git a/lib/nanoc/cli/stream_cleaners/ansi_colors.rb b/lib/nanoc/cli/stream_cleaners/ansi_colors.rb
index 00aba5bd15..9e67c19eb8 100644
--- a/lib/nanoc/cli/stream_cleaners/ansi_colors.rb
+++ b/lib/nanoc/cli/stream_cleaners/ansi_colors.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::CLI::StreamCleaners
   # Removes ANSI color escape sequences.
+  #
+  # @api private
   class ANSIColors < Abstract
     # @see Nanoc::CLI::StreamCleaners::Abstract#clean
     def clean(s)
diff --git a/lib/nanoc/cli/stream_cleaners/utf8.rb b/lib/nanoc/cli/stream_cleaners/utf8.rb
index f1727605ed..b99fa80e2e 100644
--- a/lib/nanoc/cli/stream_cleaners/utf8.rb
+++ b/lib/nanoc/cli/stream_cleaners/utf8.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::CLI::StreamCleaners
   # Simplifies output by replacing UTF-8 characters with their ASCII decompositions.
+  #
+  # @api private
   class UTF8 < Abstract
     # @see Nanoc::CLI::StreamCleaners::Abstract#clean
     def clean(s)
diff --git a/lib/nanoc/data_sources/filesystem.rb b/lib/nanoc/data_sources/filesystem.rb
index 8605e885b8..e920c22d3c 100644
--- a/lib/nanoc/data_sources/filesystem.rb
+++ b/lib/nanoc/data_sources/filesystem.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::DataSources
   # Provides functionality common across all filesystem data sources.
+  #
+  # @api private
   module Filesystem
     # The VCS that will be called when adding, deleting and moving files. If
     # no VCS has been set, or if the VCS has been set to `nil`, a dummy VCS
diff --git a/lib/nanoc/data_sources/filesystem_unified.rb b/lib/nanoc/data_sources/filesystem_unified.rb
index 36f7277df6..f2890ae55b 100644
--- a/lib/nanoc/data_sources/filesystem_unified.rb
+++ b/lib/nanoc/data_sources/filesystem_unified.rb
@@ -66,6 +66,8 @@ module Nanoc::DataSources
   # files. In the data source configuration, set `encoding` to an encoding
   # understood by Ruby’s `Encoding`. If no encoding is set in the configuration,
   # one will be inferred from the environment.
+  #
+  # @api private
   class FilesystemUnified < Nanoc::DataSource
     include Nanoc::DataSources::Filesystem
 
diff --git a/lib/nanoc/data_sources/filesystem_verbose.rb b/lib/nanoc/data_sources/filesystem_verbose.rb
index f2bea9a5d1..38a450451e 100644
--- a/lib/nanoc/data_sources/filesystem_verbose.rb
+++ b/lib/nanoc/data_sources/filesystem_verbose.rb
@@ -38,6 +38,8 @@ module Nanoc::DataSources
   # files. In the data source configuration, set `encoding` to an encoding
   # understood by Ruby’s `Encoding`. If no encoding is set in the configuration,
   # one will be inferred from the environment.
+  #
+  # @api private
   class FilesystemVerbose < Nanoc::DataSource
     include Nanoc::DataSources::Filesystem
 
diff --git a/lib/nanoc/data_sources/static.rb b/lib/nanoc/data_sources/static.rb
index 83e0926749..3122f7604f 100644
--- a/lib/nanoc/data_sources/static.rb
+++ b/lib/nanoc/data_sources/static.rb
@@ -24,6 +24,8 @@ module Nanoc::DataSources
   # data sources will have the :is_hidden attribute set by default, which will
   # exclude them from the Blogging helper's atom feed generator, among other
   # things.
+  #
+  # @api private
   class Static < Nanoc::DataSource
     identifier :static
 
diff --git a/lib/nanoc/extra.rb b/lib/nanoc/extra.rb
index bcefbca33d..3aba636ce4 100644
--- a/lib/nanoc/extra.rb
+++ b/lib/nanoc/extra.rb
@@ -1,9 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Extra
-  autoload 'AutoCompiler',        'nanoc/extra/auto_compiler'
   autoload 'Checking',            'nanoc/extra/checking'
-  autoload 'CHiCk',               'nanoc/extra/chick'
   autoload 'FilesystemTools',     'nanoc/extra/filesystem_tools'
   autoload 'LinkCollector',       'nanoc/extra/link_collector.rb'
   autoload 'Pruner',              'nanoc/extra/pruner'
diff --git a/lib/nanoc/extra/checking.rb b/lib/nanoc/extra/checking.rb
index 549e535de9..e6e56efffd 100644
--- a/lib/nanoc/extra/checking.rb
+++ b/lib/nanoc/extra/checking.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Extra
+  # @api private
   module Checking
     autoload 'Check',  'nanoc/extra/checking/check'
     autoload 'DSL',    'nanoc/extra/checking/dsl'
diff --git a/lib/nanoc/extra/checking/check.rb b/lib/nanoc/extra/checking/check.rb
index 8a0871f4dd..bf35aeedf2 100644
--- a/lib/nanoc/extra/checking/check.rb
+++ b/lib/nanoc/extra/checking/check.rb
@@ -1,12 +1,14 @@
 # encoding: utf-8
 
 module Nanoc::Extra::Checking
+  # @api private
   class OutputDirNotFoundError < Nanoc::Errors::Generic
     def initialize(directory_path)
       super("Unable to run check against output directory at “#{directory_path}”: directory does not exist.")
     end
   end
 
+  # @api private
   class Check
     extend Nanoc::PluginRegistry::PluginMethods
 
diff --git a/lib/nanoc/extra/checking/checks.rb b/lib/nanoc/extra/checking/checks.rb
index 0dd2a40e94..599241b22f 100644
--- a/lib/nanoc/extra/checking/checks.rb
+++ b/lib/nanoc/extra/checking/checks.rb
@@ -1,5 +1,6 @@
 # encoding: utf-8
 
+# @api private
 module Nanoc::Extra::Checking::Checks
   autoload 'CSS',           'nanoc/extra/checking/checks/css'
   autoload 'ExternalLinks', 'nanoc/extra/checking/checks/external_links'
diff --git a/lib/nanoc/extra/checking/checks/css.rb b/lib/nanoc/extra/checking/checks/css.rb
index a73bba05b9..7350dafacb 100644
--- a/lib/nanoc/extra/checking/checks/css.rb
+++ b/lib/nanoc/extra/checking/checks/css.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module ::Nanoc::Extra::Checking::Checks
+  # @api private
   class CSS < ::Nanoc::Extra::Checking::Check
     identifier :css
 
diff --git a/lib/nanoc/extra/checking/checks/external_links.rb b/lib/nanoc/extra/checking/checks/external_links.rb
index a1a2e537b4..8ee46b4fd9 100644
--- a/lib/nanoc/extra/checking/checks/external_links.rb
+++ b/lib/nanoc/extra/checking/checks/external_links.rb
@@ -8,6 +8,8 @@
 
 module ::Nanoc::Extra::Checking::Checks
   # A validator that verifies that all external links point to a location that exists.
+  #
+  # @api private
   class ExternalLinks < ::Nanoc::Extra::Checking::Check
     identifiers :external_links, :elinks
 
diff --git a/lib/nanoc/extra/checking/checks/html.rb b/lib/nanoc/extra/checking/checks/html.rb
index c9320649cb..c841fb9b29 100644
--- a/lib/nanoc/extra/checking/checks/html.rb
+++ b/lib/nanoc/extra/checking/checks/html.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module ::Nanoc::Extra::Checking::Checks
+  # @api private
   class HTML < ::Nanoc::Extra::Checking::Check
     identifier :html
 
diff --git a/lib/nanoc/extra/checking/checks/internal_links.rb b/lib/nanoc/extra/checking/checks/internal_links.rb
index 4e5c177269..848a316b12 100644
--- a/lib/nanoc/extra/checking/checks/internal_links.rb
+++ b/lib/nanoc/extra/checking/checks/internal_links.rb
@@ -4,6 +4,8 @@
 
 module Nanoc::Extra::Checking::Checks
   # A check that verifies that all internal links point to a location that exists.
+  #
+  # @api private
   class InternalLinks < ::Nanoc::Extra::Checking::Check
     # Starts the validator. The results will be printed to stdout.
     #
diff --git a/lib/nanoc/extra/checking/checks/mixed_content.rb b/lib/nanoc/extra/checking/checks/mixed_content.rb
index 85a6e0a153..8be9c14daf 100644
--- a/lib/nanoc/extra/checking/checks/mixed_content.rb
+++ b/lib/nanoc/extra/checking/checks/mixed_content.rb
@@ -3,6 +3,8 @@
 module Nanoc::Extra::Checking::Checks
   # A check that verifies HTML files do not reference external resources with
   # URLs that would trigger "mixed content" warnings.
+  #
+  # @api private
   class MixedContent < ::Nanoc::Extra::Checking::Check
     PROTOCOL_PATTERN = /^(\w+):\/\//
 
diff --git a/lib/nanoc/extra/checking/checks/stale.rb b/lib/nanoc/extra/checking/checks/stale.rb
index 7df56dadaf..188dd66ca6 100644
--- a/lib/nanoc/extra/checking/checks/stale.rb
+++ b/lib/nanoc/extra/checking/checks/stale.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Extra::Checking::Checks
+  # @api private
   class Stale < ::Nanoc::Extra::Checking::Check
     def run
       require 'set'
diff --git a/lib/nanoc/extra/checking/dsl.rb b/lib/nanoc/extra/checking/dsl.rb
index 97b5032030..511a436814 100644
--- a/lib/nanoc/extra/checking/dsl.rb
+++ b/lib/nanoc/extra/checking/dsl.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Extra::Checking
+  # @api private
   class DSL
     attr_reader :deploy_checks
 
diff --git a/lib/nanoc/extra/checking/issue.rb b/lib/nanoc/extra/checking/issue.rb
index b2f22c3d5b..fdafd16a3f 100644
--- a/lib/nanoc/extra/checking/issue.rb
+++ b/lib/nanoc/extra/checking/issue.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Extra::Checking
+  # @api private
   class Issue
     attr_reader :description
     attr_reader :subject
diff --git a/lib/nanoc/extra/core_ext/pathname.rb b/lib/nanoc/extra/core_ext/pathname.rb
index 73933be6b3..a35a6854a5 100644
--- a/lib/nanoc/extra/core_ext/pathname.rb
+++ b/lib/nanoc/extra/core_ext/pathname.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Extra
+  # @api private
   module PathnameExtensions
     def components
       components = []
diff --git a/lib/nanoc/extra/core_ext/time.rb b/lib/nanoc/extra/core_ext/time.rb
index 125f50b373..bce89a6e5e 100644
--- a/lib/nanoc/extra/core_ext/time.rb
+++ b/lib/nanoc/extra/core_ext/time.rb
@@ -1,5 +1,6 @@
 # encoding: utf-8
 
+# @api private
 module Nanoc::Extra::TimeExtensions
   # @return [String] The time in an ISO-8601 date format.
   def to_iso8601_date
diff --git a/lib/nanoc/extra/deployer.rb b/lib/nanoc/extra/deployer.rb
index 4d86366880..5fbdd69d89 100644
--- a/lib/nanoc/extra/deployer.rb
+++ b/lib/nanoc/extra/deployer.rb
@@ -5,6 +5,8 @@ module Nanoc::Extra
   # to a specific (remote) location.
   #
   # @abstract Subclass and override {#run} to implement a custom filter.
+  #
+  # @api private
   class Deployer
     extend Nanoc::PluginRegistry::PluginMethods
 
diff --git a/lib/nanoc/extra/deployers.rb b/lib/nanoc/extra/deployers.rb
index a1bc5acb2a..07bf90076e 100644
--- a/lib/nanoc/extra/deployers.rb
+++ b/lib/nanoc/extra/deployers.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Extra
+  # @api private
   module Deployers
     autoload 'Fog',   'nanoc/extra/deployers/fog'
     autoload 'Rsync', 'nanoc/extra/deployers/rsync'
diff --git a/lib/nanoc/extra/deployers/fog.rb b/lib/nanoc/extra/deployers/fog.rb
index 56748cdc19..67473c3e1f 100644
--- a/lib/nanoc/extra/deployers/fog.rb
+++ b/lib/nanoc/extra/deployers/fog.rb
@@ -20,6 +20,8 @@ module Nanoc::Extra::Deployers
   #       provider:   local
   #       local_root: ~/myCloud
   #       bucket:     nanoc-site-staging
+  #
+  # @api private
   class Fog < ::Nanoc::Extra::Deployer
     # @see Nanoc::Extra::Deployer#run
     def run
diff --git a/lib/nanoc/extra/deployers/rsync.rb b/lib/nanoc/extra/deployers/rsync.rb
index b768be9c06..5422fd51b7 100644
--- a/lib/nanoc/extra/deployers/rsync.rb
+++ b/lib/nanoc/extra/deployers/rsync.rb
@@ -18,6 +18,8 @@ module Nanoc::Extra::Deployers
   #       kind: rsync
   #       dst: "ectype:sites/stoneship-staging/public"
   #       options: [ "-glpPrtvz" ]
+  #
+  # @api private
   class Rsync < ::Nanoc::Extra::Deployer
     # Default rsync options
     DEFAULT_OPTIONS = [
diff --git a/lib/nanoc/extra/jruby_nokogiri_warner.rb b/lib/nanoc/extra/jruby_nokogiri_warner.rb
index 0399aaef34..1b344e80ec 100644
--- a/lib/nanoc/extra/jruby_nokogiri_warner.rb
+++ b/lib/nanoc/extra/jruby_nokogiri_warner.rb
@@ -3,6 +3,7 @@
 require 'singleton'
 
 module Nanoc::Extra
+  # @api private
   class JRubyNokogiriWarner
     include Singleton
 
diff --git a/lib/nanoc/extra/link_collector.rb b/lib/nanoc/extra/link_collector.rb
index 2a54383bf4..35e8e6e9d7 100644
--- a/lib/nanoc/extra/link_collector.rb
+++ b/lib/nanoc/extra/link_collector.rb
@@ -3,6 +3,7 @@
 require 'set'
 
 module ::Nanoc::Extra
+  # @api private
   class LinkCollector
     URI_ATTRS = {
       'a' => :href,
diff --git a/lib/nanoc/extra/piper.rb b/lib/nanoc/extra/piper.rb
index ae4bd27803..7359eea642 100644
--- a/lib/nanoc/extra/piper.rb
+++ b/lib/nanoc/extra/piper.rb
@@ -3,6 +3,7 @@
 require 'open3'
 
 module Nanoc::Extra
+  # @api private
   class Piper
     class Error < ::Nanoc::Errors::Generic
       def initialize(command, exit_code)
diff --git a/lib/nanoc/extra/pruner.rb b/lib/nanoc/extra/pruner.rb
index 9613c1343b..aeac90ec8e 100644
--- a/lib/nanoc/extra/pruner.rb
+++ b/lib/nanoc/extra/pruner.rb
@@ -3,6 +3,8 @@
 module Nanoc::Extra
   # Responsible for finding and deleting files in the site’s output directory
   # that are not managed by nanoc.
+  #
+  # @api private
   class Pruner
     # @return [Nanoc::Site] The site this pruner belongs to
     attr_reader :site
diff --git a/lib/nanoc/extra/vcs.rb b/lib/nanoc/extra/vcs.rb
index 037d756f78..b62694bd0d 100644
--- a/lib/nanoc/extra/vcs.rb
+++ b/lib/nanoc/extra/vcs.rb
@@ -8,6 +8,8 @@ module Nanoc::Extra
   #
   # @abstract Subclass and override {#add}, {#remove} and {#move} to implement
   #   a custom VCS.
+  #
+  # @api private
   class VCS
     extend Nanoc::PluginRegistry::PluginMethods
 
diff --git a/lib/nanoc/extra/vcses.rb b/lib/nanoc/extra/vcses.rb
index 26f00a3cf2..19b7569bc7 100644
--- a/lib/nanoc/extra/vcses.rb
+++ b/lib/nanoc/extra/vcses.rb
@@ -1,5 +1,6 @@
 # encoding: utf-8
 
+# @api private
 module Nanoc::Extra::VCSes
   autoload 'Bazaar',     'nanoc/extra/vcses/bazaar'
   autoload 'Dummy',      'nanoc/extra/vcses/dummy'
diff --git a/lib/nanoc/extra/vcses/bazaar.rb b/lib/nanoc/extra/vcses/bazaar.rb
index d46b50ccfc..ba116cf0d5 100644
--- a/lib/nanoc/extra/vcses/bazaar.rb
+++ b/lib/nanoc/extra/vcses/bazaar.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Extra::VCSes
   # @see Nanoc::Extra::VCS
+  #
+  # @api private
   class Bazaar < Nanoc::Extra::VCS
     # @see Nanoc::Extra::VCS#add
     def add(filename)
diff --git a/lib/nanoc/extra/vcses/dummy.rb b/lib/nanoc/extra/vcses/dummy.rb
index 7b5ab86510..32c9cc6e3b 100644
--- a/lib/nanoc/extra/vcses/dummy.rb
+++ b/lib/nanoc/extra/vcses/dummy.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Extra::VCSes
   # @see Nanoc::Extra::VCS
+  #
+  # @api private
   class Dummy < Nanoc::Extra::VCS
     # @see Nanoc::Extra::VCS#add
     def add(_filename)
diff --git a/lib/nanoc/extra/vcses/git.rb b/lib/nanoc/extra/vcses/git.rb
index e8eb6cc4b8..2aa790110c 100644
--- a/lib/nanoc/extra/vcses/git.rb
+++ b/lib/nanoc/extra/vcses/git.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Extra::VCSes
   # @see Nanoc::Extra::VCS
+  #
+  # @api private
   class Git < Nanoc::Extra::VCS
     # @see Nanoc::Extra::VCS#add
     def add(filename)
diff --git a/lib/nanoc/extra/vcses/mercurial.rb b/lib/nanoc/extra/vcses/mercurial.rb
index 05a7516d6c..cd59012b4b 100644
--- a/lib/nanoc/extra/vcses/mercurial.rb
+++ b/lib/nanoc/extra/vcses/mercurial.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Extra::VCSes
   # @see Nanoc::Extra::VCS
+  #
+  # @api private
   class Mercurial < Nanoc::Extra::VCS
     # @see Nanoc::Extra::VCS#add
     def add(filename)
diff --git a/lib/nanoc/extra/vcses/subversion.rb b/lib/nanoc/extra/vcses/subversion.rb
index 89d44bf5ea..f5cd95c463 100644
--- a/lib/nanoc/extra/vcses/subversion.rb
+++ b/lib/nanoc/extra/vcses/subversion.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Extra::VCSes
   # @see Nanoc::Extra::VCS
+  #
+  # @api private
   class Subversion < Nanoc::Extra::VCS
     # @see Nanoc::Extra::VCS#add
     def add(filename)
diff --git a/lib/nanoc/filters/asciidoc.rb b/lib/nanoc/filters/asciidoc.rb
index fa852d51ca..93027adbce 100644
--- a/lib/nanoc/filters/asciidoc.rb
+++ b/lib/nanoc/filters/asciidoc.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.2.0
+  #
+  # @api private
   class AsciiDoc < Nanoc::Filter
     # Runs the content through [AsciiDoc](http://www.methods.co.nz/asciidoc/).
     # This method takes no options.
diff --git a/lib/nanoc/filters/bluecloth.rb b/lib/nanoc/filters/bluecloth.rb
index 25f979042d..8dbfe21f9e 100644
--- a/lib/nanoc/filters/bluecloth.rb
+++ b/lib/nanoc/filters/bluecloth.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class BlueCloth < Nanoc::Filter
     requires 'bluecloth'
 
diff --git a/lib/nanoc/filters/coffeescript.rb b/lib/nanoc/filters/coffeescript.rb
index 720d36100c..2e607db1b4 100644
--- a/lib/nanoc/filters/coffeescript.rb
+++ b/lib/nanoc/filters/coffeescript.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.3.0
+  #
+  # @api private
   class CoffeeScript < Nanoc::Filter
     requires 'coffee-script'
 
diff --git a/lib/nanoc/filters/colorize_syntax.rb b/lib/nanoc/filters/colorize_syntax.rb
index 14c9975d08..2dec8f0043 100644
--- a/lib/nanoc/filters/colorize_syntax.rb
+++ b/lib/nanoc/filters/colorize_syntax.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class ColorizeSyntax < Nanoc::Filter
     requires 'nokogiri', 'stringio', 'open3'
 
diff --git a/lib/nanoc/filters/erb.rb b/lib/nanoc/filters/erb.rb
index f36aa93ebb..1ea52e10ac 100644
--- a/lib/nanoc/filters/erb.rb
+++ b/lib/nanoc/filters/erb.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class ERB < Nanoc::Filter
     requires 'erb'
 
diff --git a/lib/nanoc/filters/erubis.rb b/lib/nanoc/filters/erubis.rb
index 0286be2ec4..1f9c7308d2 100644
--- a/lib/nanoc/filters/erubis.rb
+++ b/lib/nanoc/filters/erubis.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Erubis < Nanoc::Filter
     requires 'erubis'
 
diff --git a/lib/nanoc/filters/haml.rb b/lib/nanoc/filters/haml.rb
index 54c827f18a..ecef208999 100644
--- a/lib/nanoc/filters/haml.rb
+++ b/lib/nanoc/filters/haml.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Haml < Nanoc::Filter
     requires 'haml'
 
diff --git a/lib/nanoc/filters/handlebars.rb b/lib/nanoc/filters/handlebars.rb
index 02f17929a0..7957aa65c8 100644
--- a/lib/nanoc/filters/handlebars.rb
+++ b/lib/nanoc/filters/handlebars.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.4.0
+  #
+  # @api private
   class Handlebars < Nanoc::Filter
     requires 'handlebars'
 
diff --git a/lib/nanoc/filters/kramdown.rb b/lib/nanoc/filters/kramdown.rb
index 0bbde483b3..945d072cfe 100644
--- a/lib/nanoc/filters/kramdown.rb
+++ b/lib/nanoc/filters/kramdown.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Kramdown < Nanoc::Filter
     requires 'kramdown'
 
diff --git a/lib/nanoc/filters/less.rb b/lib/nanoc/filters/less.rb
index 06dab3e6f5..c0c2344a2a 100644
--- a/lib/nanoc/filters/less.rb
+++ b/lib/nanoc/filters/less.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Less < Nanoc::Filter
     requires 'less'
 
diff --git a/lib/nanoc/filters/markaby.rb b/lib/nanoc/filters/markaby.rb
index 62a2f3d251..7c529c4b3c 100644
--- a/lib/nanoc/filters/markaby.rb
+++ b/lib/nanoc/filters/markaby.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Markaby < Nanoc::Filter
     requires 'markaby'
 
diff --git a/lib/nanoc/filters/maruku.rb b/lib/nanoc/filters/maruku.rb
index 615a4cb136..0888988c17 100644
--- a/lib/nanoc/filters/maruku.rb
+++ b/lib/nanoc/filters/maruku.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Maruku < Nanoc::Filter
     requires 'maruku'
 
diff --git a/lib/nanoc/filters/mustache.rb b/lib/nanoc/filters/mustache.rb
index 06e5a35681..9178f7e27c 100644
--- a/lib/nanoc/filters/mustache.rb
+++ b/lib/nanoc/filters/mustache.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.2.0
+  #
+  # @api private
   class Mustache < Nanoc::Filter
     requires 'mustache'
 
diff --git a/lib/nanoc/filters/pandoc.rb b/lib/nanoc/filters/pandoc.rb
index cce1a0d52b..1a39f361d9 100644
--- a/lib/nanoc/filters/pandoc.rb
+++ b/lib/nanoc/filters/pandoc.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Pandoc < Nanoc::Filter
     requires 'pandoc-ruby'
 
diff --git a/lib/nanoc/filters/rainpress.rb b/lib/nanoc/filters/rainpress.rb
index 3fd6c849b0..cf2750c878 100644
--- a/lib/nanoc/filters/rainpress.rb
+++ b/lib/nanoc/filters/rainpress.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Rainpress < Nanoc::Filter
     requires 'rainpress'
 
diff --git a/lib/nanoc/filters/rdiscount.rb b/lib/nanoc/filters/rdiscount.rb
index ecf5b529a7..d016b4bcf1 100644
--- a/lib/nanoc/filters/rdiscount.rb
+++ b/lib/nanoc/filters/rdiscount.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class RDiscount < Nanoc::Filter
     requires 'rdiscount'
 
diff --git a/lib/nanoc/filters/rdoc.rb b/lib/nanoc/filters/rdoc.rb
index 12b0f6acb6..e1e6b1a270 100644
--- a/lib/nanoc/filters/rdoc.rb
+++ b/lib/nanoc/filters/rdoc.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class RDoc < Nanoc::Filter
     requires 'rdoc'
 
diff --git a/lib/nanoc/filters/redcarpet.rb b/lib/nanoc/filters/redcarpet.rb
index 5a53dc2039..b637a141e4 100644
--- a/lib/nanoc/filters/redcarpet.rb
+++ b/lib/nanoc/filters/redcarpet.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.2.0
+  #
+  # @api private
   class Redcarpet < Nanoc::Filter
     requires 'redcarpet'
 
diff --git a/lib/nanoc/filters/redcloth.rb b/lib/nanoc/filters/redcloth.rb
index c50c522c51..69f603b703 100644
--- a/lib/nanoc/filters/redcloth.rb
+++ b/lib/nanoc/filters/redcloth.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class RedCloth < Nanoc::Filter
     requires 'redcloth'
 
diff --git a/lib/nanoc/filters/relativize_paths.rb b/lib/nanoc/filters/relativize_paths.rb
index 707c484377..8838eca437 100644
--- a/lib/nanoc/filters/relativize_paths.rb
+++ b/lib/nanoc/filters/relativize_paths.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class RelativizePaths < Nanoc::Filter
     require 'nanoc/helpers/link_to'
     include Nanoc::Helpers::LinkTo
diff --git a/lib/nanoc/filters/rubypants.rb b/lib/nanoc/filters/rubypants.rb
index 321a8a0d4d..a3daa76251 100644
--- a/lib/nanoc/filters/rubypants.rb
+++ b/lib/nanoc/filters/rubypants.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class RubyPants < Nanoc::Filter
     requires 'rubypants'
 
diff --git a/lib/nanoc/filters/sass.rb b/lib/nanoc/filters/sass.rb
index 02f9d1e498..819b2e0e4b 100644
--- a/lib/nanoc/filters/sass.rb
+++ b/lib/nanoc/filters/sass.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class Sass < Nanoc::Filter
     requires 'sass', 'nanoc/filters/sass/sass_filesystem_importer'
 
diff --git a/lib/nanoc/filters/sass/sass_filesystem_importer.rb b/lib/nanoc/filters/sass/sass_filesystem_importer.rb
index 2f95ffc53a..cfd2c35cb1 100644
--- a/lib/nanoc/filters/sass/sass_filesystem_importer.rb
+++ b/lib/nanoc/filters/sass/sass_filesystem_importer.rb
@@ -1,5 +1,6 @@
 # encoding: utf-8
 
+# @api private
 class ::Sass::Importers::Filesystem
   alias_method :_orig_find, :_find
 
diff --git a/lib/nanoc/filters/slim.rb b/lib/nanoc/filters/slim.rb
index e15a0fa09e..40b4b591a8 100644
--- a/lib/nanoc/filters/slim.rb
+++ b/lib/nanoc/filters/slim.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.2.0
+  #
+  # @api private
   class Slim < Nanoc::Filter
     requires 'slim'
 
diff --git a/lib/nanoc/filters/typogruby.rb b/lib/nanoc/filters/typogruby.rb
index 47de9b19ce..a19d2ca305 100644
--- a/lib/nanoc/filters/typogruby.rb
+++ b/lib/nanoc/filters/typogruby.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.2.0
+  #
+  # @api private
   class Typogruby < Nanoc::Filter
     requires 'typogruby'
 
diff --git a/lib/nanoc/filters/uglify_js.rb b/lib/nanoc/filters/uglify_js.rb
index 4024acc935..3d410714c8 100644
--- a/lib/nanoc/filters/uglify_js.rb
+++ b/lib/nanoc/filters/uglify_js.rb
@@ -1,6 +1,7 @@
 # encoding: utf-8
 
 module Nanoc::Filters
+  # @api private
   class UglifyJS < Nanoc::Filter
     requires 'uglifier'
 
diff --git a/lib/nanoc/filters/xsl.rb b/lib/nanoc/filters/xsl.rb
index 5dede2da8c..e74a440aa6 100644
--- a/lib/nanoc/filters/xsl.rb
+++ b/lib/nanoc/filters/xsl.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.3.0
+  #
+  # @api private
   class XSL < Nanoc::Filter
     requires 'nokogiri'
 
diff --git a/lib/nanoc/filters/yui_compressor.rb b/lib/nanoc/filters/yui_compressor.rb
index 5b3438ee49..1f917fbe57 100644
--- a/lib/nanoc/filters/yui_compressor.rb
+++ b/lib/nanoc/filters/yui_compressor.rb
@@ -2,6 +2,8 @@
 
 module Nanoc::Filters
   # @since 3.3.0
+  #
+  # @api private
   class YUICompressor < Nanoc::Filter
     requires 'yuicompressor'