diff --git a/Gemfile b/Gemfile
index 07c300510c..355b7e43f8 100644
--- a/Gemfile
+++ b/Gemfile
@@ -122,6 +122,7 @@ group :test do
   gem 'simplecov', '~> 0.21', require: false
   gem 'webmock', '~> 3.18'
   gem 'rspec_junit_formatter', '~> 0.6'
+  gem 'rack-test', '~> 2.0'
 end
 
 group :development do
@@ -152,7 +153,5 @@ end
 
 gem 'concurrent-ruby', require: false
 gem 'connection_pool', require: false
-
 gem 'xorcist', '~> 1.1'
-
 gem 'cocoon', '~> 1.2'
diff --git a/Gemfile.lock b/Gemfile.lock
index 28c6e73481..87d07b6312 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -815,6 +815,7 @@ DEPENDENCIES
   rack (~> 2.2.4)
   rack-attack (~> 6.6)
   rack-cors (~> 1.1)
+  rack-test (~> 2.0)
   rails (~> 6.1.7)
   rails-controller-testing (~> 1.0)
   rails-i18n (~> 6.0)
diff --git a/config/initializers/rack_attack.rb b/config/initializers/rack_attack.rb
index 745eb5d3bf..72ef7ba801 100644
--- a/config/initializers/rack_attack.rb
+++ b/config/initializers/rack_attack.rb
@@ -17,6 +17,18 @@ class Rack::Attack
       @remote_ip ||= (@env["action_dispatch.remote_ip"] || ip).to_s
     end
 
+    def throttleable_remote_ip
+      @throttleable_remote_ip ||= begin
+        ip = IPAddr.new(remote_ip)
+
+        if ip.ipv6?
+          ip.mask(64)
+        else
+          ip
+        end
+      end.to_s
+    end
+
     def authenticated_user_id
       authenticated_token&.resource_owner_id
     end
@@ -29,6 +41,10 @@ class Rack::Attack
       path.start_with?('/api')
     end
 
+    def path_matches?(other_path)
+      /\A#{Regexp.escape(other_path)}(\..*)?\z/ =~ path
+    end
+
     def web_request?
       !api_request?
     end
@@ -51,19 +67,19 @@ class Rack::Attack
   end
 
   throttle('throttle_unauthenticated_api', limit: 300, period: 5.minutes) do |req|
-    req.remote_ip if req.api_request? && req.unauthenticated?
+    req.throttleable_remote_ip if req.api_request? && req.unauthenticated?
   end
 
   throttle('throttle_api_media', limit: 30, period: 30.minutes) do |req|
-    req.authenticated_user_id if req.post? && req.path.match?('^/api/v\d+/media')
+    req.authenticated_user_id if req.post? && req.path.match?(/\A\/api\/v\d+\/media\z/i)
   end
 
   throttle('throttle_media_proxy', limit: 30, period: 10.minutes) do |req|
-    req.remote_ip if req.path.start_with?('/media_proxy')
+    req.throttleable_remote_ip if req.path.start_with?('/media_proxy')
   end
 
   throttle('throttle_api_sign_up', limit: 5, period: 30.minutes) do |req|
-    req.remote_ip if req.post? && req.path == '/api/v1/accounts'
+    req.throttleable_remote_ip if req.post? && req.path == '/api/v1/accounts'
   end
 
   throttle('throttle_authenticated_paging', limit: 300, period: 15.minutes) do |req|
@@ -71,39 +87,34 @@ class Rack::Attack
   end
 
   throttle('throttle_unauthenticated_paging', limit: 300, period: 15.minutes) do |req|
-    req.remote_ip if req.paging_request? && req.unauthenticated?
+    req.throttleable_remote_ip if req.paging_request? && req.unauthenticated?
   end
 
-  API_DELETE_REBLOG_REGEX = /\A\/api\/v1\/statuses\/[\d]+\/unreblog/.freeze
-  API_DELETE_STATUS_REGEX = /\A\/api\/v1\/statuses\/[\d]+/.freeze
+  API_DELETE_REBLOG_REGEX = /\A\/api\/v1\/statuses\/[\d]+\/unreblog\z/.freeze
+  API_DELETE_STATUS_REGEX = /\A\/api\/v1\/statuses\/[\d]+\z/.freeze
 
   throttle('throttle_api_delete', limit: 30, period: 30.minutes) do |req|
     req.authenticated_user_id if (req.post? && req.path.match?(API_DELETE_REBLOG_REGEX)) || (req.delete? && req.path.match?(API_DELETE_STATUS_REGEX))
   end
 
   throttle('throttle_sign_up_attempts/ip', limit: 25, period: 5.minutes) do |req|
-    if req.post? && req.path == '/auth'
-      addr = req.remote_ip
-      addr = IPAddr.new(addr) if addr.is_a?(String)
-      addr = addr.mask(64) if addr.ipv6?
-      addr.to_s
-    end
+    req.throttleable_remote_ip if req.post? && req.path_matches?('/auth')
   end
 
   throttle('throttle_password_resets/ip', limit: 25, period: 5.minutes) do |req|
-    req.remote_ip if req.post? && req.path == '/auth/password'
+    req.throttleable_remote_ip if req.post? && req.path_matches?('/auth/password')
   end
 
   throttle('throttle_password_resets/email', limit: 5, period: 30.minutes) do |req|
-    req.params.dig('user', 'email').presence if req.post? && req.path == '/auth/password'
+    req.params.dig('user', 'email').presence if req.post? && req.path_matches?('/auth/password')
   end
 
   throttle('throttle_email_confirmations/ip', limit: 25, period: 5.minutes) do |req|
-    req.remote_ip if req.post? && %w(/auth/confirmation /api/v1/emails/confirmations).include?(req.path)
+    req.throttleable_remote_ip if req.post? && (req.path_matches?('/auth/confirmation') || req.path == '/api/v1/emails/confirmations')
   end
 
   throttle('throttle_email_confirmations/email', limit: 5, period: 30.minutes) do |req|
-    if req.post? && req.path == '/auth/password'
+    if req.post? && req.path_matches?('/auth/password')
       req.params.dig('user', 'email').presence
     elsif req.post? && req.path == '/api/v1/emails/confirmations'
       req.authenticated_user_id
@@ -111,11 +122,11 @@ class Rack::Attack
   end
 
   throttle('throttle_login_attempts/ip', limit: 25, period: 5.minutes) do |req|
-    req.remote_ip if req.post? && req.path == '/auth/sign_in'
+    req.throttleable_remote_ip if req.post? && req.path_matches?('/auth/sign_in')
   end
 
   throttle('throttle_login_attempts/email', limit: 25, period: 1.hour) do |req|
-    req.session[:attempt_user_id] || req.params.dig('user', 'email').presence if req.post? && req.path == '/auth/sign_in'
+    req.session[:attempt_user_id] || req.params.dig('user', 'email').presence if req.post? && req.path_matches?('/auth/sign_in')
   end
 
   self.throttled_responder = lambda do |request|
diff --git a/config/routes.rb b/config/routes.rb
index f095ff6551..98aa5a0330 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -73,7 +73,7 @@ Rails.application.routes.draw do
     end
   end
 
-  devise_for :users, path: 'auth', controllers: {
+  devise_for :users, path: 'auth', format: false, controllers: {
     omniauth_callbacks: 'auth/omniauth_callbacks',
     sessions:           'auth/sessions',
     registrations:      'auth/registrations',
@@ -216,7 +216,7 @@ Rails.application.routes.draw do
   resource :relationships, only: [:show, :update]
   resource :statuses_cleanup, controller: :statuses_cleanup, only: [:show, :update]
 
-  get '/media_proxy/:id/(*any)', to: 'media_proxy#show', as: :media_proxy
+  get '/media_proxy/:id/(*any)', to: 'media_proxy#show', as: :media_proxy, format: false
 
   resource :authorize_interaction, only: [:show, :create]
   resource :share, only: [:show, :create]
@@ -404,7 +404,7 @@ Rails.application.routes.draw do
 
   get '/admin', to: redirect('/admin/dashboard', status: 302)
 
-  namespace :api do
+  namespace :api, format: false do
     # OEmbed
     get '/oembed', to: 'oembed#show', as: :oembed
 
diff --git a/spec/config/initializers/rack_attack_spec.rb b/spec/config/initializers/rack_attack_spec.rb
new file mode 100644
index 0000000000..581021cb90
--- /dev/null
+++ b/spec/config/initializers/rack_attack_spec.rb
@@ -0,0 +1,82 @@
+require 'rails_helper'
+
+describe Rack::Attack do
+  include Rack::Test::Methods
+
+  def app
+    Rails.application
+  end
+
+  shared_examples 'throttled endpoint' do
+    context 'when the number of requests is lower than the limit' do
+      it 'does not change the request status' do
+        limit.times do
+          request.call
+          expect(last_response.status).to_not eq(429)
+        end
+      end
+    end
+
+    context 'when the number of requests is higher than the limit' do
+      it 'returns http too many requests' do
+        (limit * 2).times do |i|
+          request.call
+          expect(last_response.status).to eq(429) if i > limit
+        end
+      end
+    end
+  end
+
+  let(:remote_ip) { '1.2.3.5' }
+
+  describe 'throttle excessive sign-up requests by IP address' do
+    context 'through the website' do
+      let(:limit) { 25 }
+      let(:request) { ->() { post path, {}, 'REMOTE_ADDR' => remote_ip } }
+
+      context 'for exact path' do
+        let(:path)  { '/auth' }
+        it_behaves_like 'throttled endpoint'
+      end
+
+      context 'for path with format' do
+        let(:path)  { '/auth.html' }
+        it_behaves_like 'throttled endpoint'
+      end
+    end
+
+    context 'through the API' do
+      let(:limit) { 5 }
+      let(:request) { ->() { post path, {}, 'REMOTE_ADDR' => remote_ip } }
+
+      context 'for exact path' do
+        let(:path)  { '/api/v1/accounts' }
+        it_behaves_like 'throttled endpoint'
+      end
+
+      context 'for path with format' do
+        let(:path)  { '/api/v1/accounts.json' }
+
+        it 'returns http not found' do
+          request.call
+          expect(last_response.status).to eq(404)
+        end
+      end
+    end
+  end
+
+  describe 'throttle excessive sign-in requests by IP address' do
+    let(:limit) { 25 }
+    let(:request) { ->() { post path, {}, 'REMOTE_ADDR' => remote_ip } }
+
+    context 'for exact path' do
+      let(:path)  { '/auth/sign_in' }
+      it_behaves_like 'throttled endpoint'
+    end
+
+    context 'for path with format' do
+      let(:path)  { '/auth/sign_in.html' }
+      it_behaves_like 'throttled endpoint'
+    end
+  end
+end