diff --git a/Dockerfile b/Dockerfile
index 6949da3fb..d1360160c 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -28,21 +28,23 @@ ENV LANG=en_US.UTF-8
 ENV LANGUAGE=en_US:en
 ENV LC_ALL=en_US.UTF-8
 
-ENV BUNDLER_VERSION=2.5.11
-RUN gem install bundler -v ${BUNDLER_VERSION} -i /usr/local/lib/ruby/gems/$(ls /usr/local/lib/ruby/gems) --force
-
 WORKDIR /srv
 
-COPY Gemfile doorkeeper.gemspec /srv/
-COPY lib/doorkeeper/version.rb /srv/lib/doorkeeper/version.rb
-
-RUN bundle install
-
 COPY . /srv/
 
-RUN chown -R doorkeeper:doorkeeper /srv/coverage
+RUN chown -R doorkeeper:doorkeeper /srv
 
 # Set the running user for resulting container
 USER doorkeeper
 
-CMD ["rake"]
+RUN mkdir -p /srv/.local/gem/share
+ENV GEM_HOME=/srv/.local/gem/share
+
+ENV BUNDLER_VERSION=2.5.11
+RUN gem install bundler -v ${BUNDLER_VERSION}
+
+# This is a fix for sqlite alpine issues
+RUN bundle config force_ruby_platform true
+RUN bundle install
+
+CMD ["bundle", "exec", "rake"]
diff --git a/Gemfile b/Gemfile
index 346bc323d..03399e08e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -27,3 +27,8 @@ gem "sqlite3", "~> 1.4", platform: [:ruby, :mswin, :mingw, :x64_mingw]
 
 gem "tzinfo-data", platforms: %i[mingw mswin x64_mingw]
 gem "timecop"
+
+gem 'irb', '~> 1.8'
+
+# Interactive Debugging tools
+gem 'debug', '~> 1.8'
diff --git a/app/controllers/doorkeeper/discovery_controller.rb b/app/controllers/doorkeeper/discovery_controller.rb
new file mode 100644
index 000000000..d58cd9fbb
--- /dev/null
+++ b/app/controllers/doorkeeper/discovery_controller.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module Doorkeeper
+  class DiscoveryController < Doorkeeper::ApplicationMetalController
+    def show
+      render json: {}, status: 200
+    end
+  end
+end
diff --git a/bin/console b/bin/console
index 019ffb0df..df716fecf 100755
--- a/bin/console
+++ b/bin/console
@@ -4,15 +4,10 @@
 require "bundler/setup"
 require "rails/all"
 require "active_support/all"
+require "irb"
+require "debug"
 require "doorkeeper"
 
-# You can add fixtures and/or initialization code here to make experimenting
-# with your gem easier. You can also use a different console, if you like.
-
-# (If you use this, don't forget to add pry to your Gemfile!)
-# require "pry"
-# Pry.start
-
 Rails.logger = Logger.new(STDOUT)
 
 Rails.logger.info("Doorkeeper version: #{Doorkeeper::VERSION::STRING}")
@@ -32,5 +27,4 @@ ActiveRecord::Base.establish_connection(
 # Load database schema
 load File.expand_path("../spec/dummy/db/schema.rb", __dir__)
 
-require "irb"
 IRB.start(__FILE__)
diff --git a/lib/doorkeeper/config.rb b/lib/doorkeeper/config.rb
index d8d8ce88a..eaa226c75 100644
--- a/lib/doorkeeper/config.rb
+++ b/lib/doorkeeper/config.rb
@@ -243,6 +243,7 @@ def configure_secrets_for(type, using:, fallback:)
     option :orm,                            default: :active_record
     option :native_redirect_uri,            default: "urn:ietf:wg:oauth:2.0:oob", deprecated: true
     option :grant_flows,                    default: %w[authorization_code client_credentials]
+    option :pkce_code_challenge_methods,    default: %w[plain S256]
     option :handle_auth_errors,             default: :render
     option :token_lookup_batch_size,        default: 10_000
     # Sets the token_reuse_limit
@@ -554,6 +555,12 @@ def scopes_by_grant_type
       @scopes_by_grant_type ||= {}
     end
 
+    def pkce_code_challenge_methods_supported
+      return [] unless access_grant_model.pkce_supported?
+      
+      pkce_code_challenge_methods
+    end
+
     def client_credentials_methods
       @client_credentials_methods ||= %i[from_basic from_params]
     end
diff --git a/lib/doorkeeper/config/validations.rb b/lib/doorkeeper/config/validations.rb
index bf9760014..d7ee68659 100644
--- a/lib/doorkeeper/config/validations.rb
+++ b/lib/doorkeeper/config/validations.rb
@@ -11,6 +11,7 @@ def validate!
         validate_reuse_access_token_value
         validate_token_reuse_limit
         validate_secret_strategies
+        validate_pkce_code_challenge_methods
       end
 
       private
@@ -48,6 +49,17 @@ def validate_token_reuse_limit
         )
         @token_reuse_limit = 100
       end
+
+      def validate_pkce_code_challenge_methods
+        return if pkce_code_challenge_methods.all? {|method| method =~ /^plain$|^S256$/ }
+
+        ::Rails.logger.warn(
+          "[DOORKEEPER] You have configured an invalid value for pkce_code_challenge_methods option. " \
+          "It will be set to default ['plain', 'S256']",
+        )
+
+        @pkce_code_challenge_methods = ['plain', 'S256']
+      end
     end
   end
 end
diff --git a/lib/doorkeeper/oauth/pre_authorization.rb b/lib/doorkeeper/oauth/pre_authorization.rb
index 88f744bb4..050bc2d4f 100644
--- a/lib/doorkeeper/oauth/pre_authorization.rb
+++ b/lib/doorkeeper/oauth/pre_authorization.rb
@@ -154,7 +154,7 @@ def validate_code_challenge_method
         return true unless Doorkeeper.config.access_grant_model.pkce_supported?
 
         code_challenge.blank? ||
-          (code_challenge_method.present? && code_challenge_method =~ /^plain$|^S256$/)
+          (code_challenge_method.present? && Doorkeeper.config.pkce_code_challenge_methods_supported.include?(code_challenge_method))
       end
 
       def response_on_fragment?
diff --git a/lib/doorkeeper/rails/routes.rb b/lib/doorkeeper/rails/routes.rb
index 1a2bf7c48..3d0cf58d4 100644
--- a/lib/doorkeeper/rails/routes.rb
+++ b/lib/doorkeeper/rails/routes.rb
@@ -41,10 +41,16 @@ def generate_routes!(options)
           map_route(:authorized_applications, :authorized_applications_routes)
           map_route(:token_info, :token_info_routes)
         end
+
+        map_route(:discovery, :discovery_routes)
       end
 
       private
 
+      def discovery_routes(mapping)
+        routes.get ".well-known/oauth-authorization-server", controller: mapping[:controllers], action: :show
+      end
+
       def authorization_routes(mapping)
         routes.resource(
           :authorization,
diff --git a/lib/doorkeeper/rails/routes/mapping.rb b/lib/doorkeeper/rails/routes/mapping.rb
index eac2f12b1..90e6d85cb 100644
--- a/lib/doorkeeper/rails/routes/mapping.rb
+++ b/lib/doorkeeper/rails/routes/mapping.rb
@@ -11,6 +11,7 @@ def initialize
             authorizations: "doorkeeper/authorizations",
             applications: "doorkeeper/applications",
             authorized_applications: "doorkeeper/authorized_applications",
+            discovery: "doorkeeper/discovery",
             tokens: "doorkeeper/tokens",
             token_info: "doorkeeper/token_info",
           }
diff --git a/spec/dummy/app/controllers/custom_discovery_controller.rb b/spec/dummy/app/controllers/custom_discovery_controller.rb
new file mode 100644
index 000000000..97a0a77b7
--- /dev/null
+++ b/spec/dummy/app/controllers/custom_discovery_controller.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class CustomDiscoveryController < ::ApplicationController
+  def show
+    render nothing: true
+  end
+end
diff --git a/spec/lib/oauth/authorization_code_request_spec.rb b/spec/lib/oauth/authorization_code_request_spec.rb
index ae5cf66ab..cca21867f 100644
--- a/spec/lib/oauth/authorization_code_request_spec.rb
+++ b/spec/lib/oauth/authorization_code_request_spec.rb
@@ -231,6 +231,28 @@
 
         expect(request.error).to eq(Doorkeeper::Errors::InvalidGrant)
       end
+
+      context "when PKCE code challenge methods is set to only S256" do
+        before do
+          Doorkeeper.configure do
+            pkce_code_challenge_methods ["S256"]
+          end
+        end
+
+        it "validates when code_verifier is S256" do
+          params[:code_verifier] = grant.code_challenge = "S256"
+          request.validate
+
+          expect(request.error).to eq(nil)
+        end
+
+        it "invalidates when code_verifier is plain" do
+          params[:code_verifier] = "plain"
+          request.validate
+
+          expect(request.error).to eq(Doorkeeper::Errors::InvalidGrant)
+        end
+      end
     end
 
     context "when PKCE is not supported" do
diff --git a/spec/lib/oauth/pre_authorization_spec.rb b/spec/lib/oauth/pre_authorization_spec.rb
index 9aa561ffd..3ee631a4b 100644
--- a/spec/lib/oauth/pre_authorization_spec.rb
+++ b/spec/lib/oauth/pre_authorization_spec.rb
@@ -330,6 +330,28 @@
 
         expect(pre_auth).not_to be_authorizable
       end
+
+      context "when pkce_code_challenge_methods is set to only S256" do
+        before do
+          Doorkeeper.configure do
+            pkce_code_challenge_methods ["S256"]
+          end
+        end
+
+        it "accepts S256 as a code_challenge_method" do
+          attributes[:code_challenge] = "a45a9fea-0676-477e-95b1-a40f72ac3cfb"
+          attributes[:code_challenge_method] = "S256"
+
+          expect(pre_auth).to be_authorizable
+        end
+
+        it "rejects plain as a code_challenge_method" do
+          attributes[:code_challenge] = "a45a9fea-0676-477e-95b1-a40f72ac3cfb"
+          attributes[:code_challenge_method] = "plain"
+
+          expect(pre_auth).to_not be_authorizable
+        end
+      end
     end
 
     context "when PKCE is not supported" do
diff --git a/spec/requests/endpoints/discovery_spec.rb b/spec/requests/endpoints/discovery_spec.rb
new file mode 100644
index 000000000..295d011b1
--- /dev/null
+++ b/spec/requests/endpoints/discovery_spec.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+RSpec.describe "Discovery endpoint" do
+  it "returns json" do
+    get "/.well-known/oauth-authorization-server"
+
+    response_status_should_be(200)
+
+    # WIP: currently empty
+    expect(json_response).to eq({})
+  end
+end
diff --git a/spec/routing/custom_controller_routes_spec.rb b/spec/routing/custom_controller_routes_spec.rb
index 48788f532..8cd2a9f0e 100644
--- a/spec/routing/custom_controller_routes_spec.rb
+++ b/spec/routing/custom_controller_routes_spec.rb
@@ -16,7 +16,8 @@
           controllers authorizations: "custom_authorizations",
                       tokens: "custom_authorizations",
                       applications: "custom_authorizations",
-                      token_info: "custom_authorizations"
+                      token_info: "custom_authorizations",
+                      discovery: "custom_discovery"
 
           as authorizations: "custom_auth",
              tokens: "custom_token",
@@ -29,7 +30,8 @@
           controllers authorizations: "custom_authorizations",
                       tokens: "custom_authorizations",
                       applications: "custom_authorizations",
-                      token_info: "custom_authorizations"
+                      token_info: "custom_authorizations",
+                      discovery: "custom_discovery"
 
           as authorizations: "custom_auth",
              tokens: "custom_token",
@@ -41,7 +43,8 @@
         use_doorkeeper do
           controllers authorizations: "custom_authorizations",
                       tokens: "custom_authorizations",
-                      token_info: "custom_authorizations"
+                      token_info: "custom_authorizations",
+                      discovery: "custom_discovery"
 
           as authorizations: "custom_auth",
              tokens: "custom_token",
@@ -83,6 +86,11 @@
     expect(get("/inner_space/scope/token/info")).to route_to("custom_authorizations#show")
   end
 
+  it "GET /inner_space/.well-known/oauth-authorization-server route to show Discovery controller" do
+    expect(get("/space/.well-known/oauth-authorization-server")).to route_to("custom_discovery#show")
+  end
+
+
   it "GET /space/oauth/authorize routes to custom authorizations controller" do
     expect(get("/space/oauth/authorize")).to route_to("custom_authorizations#new")
   end
@@ -115,6 +123,10 @@
     expect(get("/space/oauth/token/info")).to route_to("custom_authorizations#show")
   end
 
+  it "GET /space/.well-known/oauth-authorization-server route to show Discovery controller" do
+    expect(get("/space/.well-known/oauth-authorization-server")).to route_to("custom_discovery#show")
+  end
+
   it "POST /outer_space/oauth/token is not be routable" do
     expect(post("/outer_space/oauth/token")).not_to be_routable
   end
@@ -130,4 +142,8 @@
   it "GET /outer_space/oauth/token_info is not routable" do
     expect(get("/outer_space/oauth/token/info")).not_to be_routable
   end
+
+  it "GET /outer_space/.well-known/oauth-authorization-server route to show Discovery controller" do
+    expect(get("/outer_space/.well-known/oauth-authorization-server")).to route_to("custom_discovery#show")
+  end
 end
diff --git a/spec/routing/default_routes_spec.rb b/spec/routing/default_routes_spec.rb
index 0793b5341..ca6f16f54 100644
--- a/spec/routing/default_routes_spec.rb
+++ b/spec/routing/default_routes_spec.rb
@@ -38,4 +38,8 @@
   it "GET /oauth/token/info route to authorized TokenInfo controller" do
     expect(get("/oauth/token/info")).to route_to("doorkeeper/token_info#show")
   end
+
+  it "GET /.well-known/oauth-authorization-server route to show Discovery controller" do
+    expect(get("/.well-known/oauth-authorization-server")).to route_to("doorkeeper/discovery#show")
+  end
 end
diff --git a/spec/routing/scoped_routes_spec.rb b/spec/routing/scoped_routes_spec.rb
index 3a0be6eb4..8f3584a6d 100644
--- a/spec/routing/scoped_routes_spec.rb
+++ b/spec/routing/scoped_routes_spec.rb
@@ -53,4 +53,8 @@
   it "POST /scope/introspect routes not to exist" do
     expect(post("/scope/introspect")).not_to be_routable
   end
+
+  it "GET /.well-known/oauth-authorization-server route to show Discovery controller" do
+    expect(get("/.well-known/oauth-authorization-server")).to route_to("doorkeeper/discovery#show")
+  end
 end