diff --git a/CHANGELOG.md b/CHANGELOG.md
index f084c97..aed1d80 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Added
 ### Changed
+- Update swagger-ui version to 3.23.11 [#239](https://github.com/rswag/rswag/pull/239)
 ### Deprecated
 ### Removed
 ### Fixed
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 65c7c47..84ae9df 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -55,6 +55,19 @@ Push to your fork and [submit a Pull Request][pr].
 
 [pr]: https://github.com/rswag/rswag/compare/
 
+## Updating Swagger UI
+
+Find the latest versions of swagger-ui here:  
+https://github.com/swagger-api/swagger-ui/releases
+
+Update the swagger-ui-dist version in the rswag-ui dependencies
+```  
+./rswag-ui/package.json
+```
+
+Navigate to the rswag-ui folder and run npm install to update the package-lock.json
+
+
 ## Release
 (for maintainers)
 
diff --git a/Gemfile b/Gemfile
index c8d0b12..38bb3ad 100644
--- a/Gemfile
+++ b/Gemfile
@@ -27,9 +27,10 @@ gem 'rswag-ui', path: './rswag-ui'
 
 group :test do
   gem 'capybara'
-  gem 'capybara-webkit'
+  gem 'geckodriver-helper'
   gem 'generator_spec'
   gem 'rspec-rails'
+  gem 'selenium-webdriver'
   gem 'rswag-specs', path: './rswag-specs'
   gem 'test-unit'
 end
diff --git a/README.md b/README.md
index 3038a6a..11c452b 100644
--- a/README.md
+++ b/README.md
@@ -768,6 +768,21 @@ end
 
 Note how the filter is passed the rack env for the current request. This provides a lot of flexibilty. For example, you can assign the "host" property (as shown) or you could inspect session information or an Authorization header and remove operations based on user permissions.
 
+### Custom Headers for Swagger Files ###
+
+You can specify custom headers for serving your generated Swagger JSON. For example you may want to force a specific charset for the 'Content-Type' header. You can configure a hash of headers to be sent with the request:
+
+```ruby
+Rswag::Api.configure do |c|
+  ...
+  
+  c.swagger_headers = { 'Content-Type' => 'application/json; charset=UTF-8' }
+end
+```
+
+Take care when overriding Content-Type if you serve both YAML and JSON files as it will no longer switch the Content-Type header correctly.
+
+
 ### Enable Swagger Endpoints for swagger-ui ###
 
 You can update the _rswag-ui.rb_ initializer, installed with rswag-ui, to specify which Swagger endpoints should be available to power the documentation UI. If you're using rswag-api, these should correspond to the Swagger endpoints it exposes. When the UI is rendered, you'll see these listed in a drop-down to the top right of the page:
diff --git a/rswag-api/lib/rswag/api/configuration.rb b/rswag-api/lib/rswag/api/configuration.rb
index ff56180..bf64229 100644
--- a/rswag-api/lib/rswag/api/configuration.rb
+++ b/rswag-api/lib/rswag/api/configuration.rb
@@ -1,7 +1,7 @@
 module Rswag
   module Api
     class Configuration
-      attr_accessor :swagger_root, :swagger_filter
+      attr_accessor :swagger_root, :swagger_filter, :swagger_headers
 
       def resolve_swagger_root(env)
         path_params = env['action_dispatch.request.path_parameters'] || {}
diff --git a/rswag-api/lib/rswag/api/middleware.rb b/rswag-api/lib/rswag/api/middleware.rb
index 637d42d..77a3b01 100644
--- a/rswag-api/lib/rswag/api/middleware.rb
+++ b/rswag-api/lib/rswag/api/middleware.rb
@@ -19,11 +19,12 @@ module Rswag
           swagger = parse_file(filename)
           @config.swagger_filter.call(swagger, env) unless @config.swagger_filter.nil?
           mime = Rack::Mime.mime_type(::File.extname(path), 'text/plain')
+          headers = { 'Content-Type' => mime }.merge(@config.swagger_headers || {})
           body = unload_swagger(filename, swagger)
 
           return [
             '200',
-            { 'Content-Type' => mime },
+            headers,
             [ body ]
           ]
         end
diff --git a/rswag-api/spec/rswag/api/middleware_spec.rb b/rswag-api/spec/rswag/api/middleware_spec.rb
index e8cc23a..6f90724 100644
--- a/rswag-api/spec/rswag/api/middleware_spec.rb
+++ b/rswag-api/spec/rswag/api/middleware_spec.rb
@@ -37,6 +37,42 @@ module Rswag
           end
         end
 
+        context 'when swagger_headers is configured' do
+          let(:env) { env_defaults.merge('PATH_INFO' => 'v1/swagger.json') }
+
+          context 'replacing the default content type header' do
+            before do
+              config.swagger_headers = { 'Content-Type' => 'application/json; charset=UTF-8' }
+            end
+            it 'returns a 200 status' do
+              expect(response.length).to eql(3)
+              expect(response.first).to eql('200')
+            end
+
+            it 'applies the headers to the response' do
+              expect(response[1]).to include( 'Content-Type' => 'application/json; charset=UTF-8')
+            end
+          end
+
+          context 'adding an additional header' do
+            before do
+              config.swagger_headers = { 'Access-Control-Allow-Origin' => '*' }
+            end
+            it 'returns a 200 status' do
+              expect(response.length).to eql(3)
+              expect(response.first).to eql('200')
+            end
+
+            it 'applies the headers to the response' do
+              expect(response[1]).to include( 'Access-Control-Allow-Origin' => '*')
+            end
+
+            it 'keeps the default header' do
+              expect(response[1]).to include( 'Content-Type' => 'application/json')
+            end
+          end
+        end
+
         context "given a path that doesn't map to any swagger file" do
           let(:env) { env_defaults.merge('PATH_INFO' => 'foobar.json') }
           before do
diff --git a/rswag-ui/package-lock.json b/rswag-ui/package-lock.json
index 144573b..8bc72e8 100644
--- a/rswag-ui/package-lock.json
+++ b/rswag-ui/package-lock.json
@@ -5,9 +5,9 @@
   "requires": true,
   "dependencies": {
     "swagger-ui-dist": {
-      "version": "3.18.2",
-      "resolved": "https://registry.npmjs.org/swagger-ui-dist/-/swagger-ui-dist-3.18.2.tgz",
-      "integrity": "sha512-pWAEiKkgWUJvjmLW9AojudnutJ+NTn5g6OdNLj1iIJWwCkoy40K3Upwa24DqFbmIE4vLX4XplND61hp2L+s5vg=="
+      "version": "3.23.11",
+      "resolved": "https://registry.npmjs.org/swagger-ui-dist/-/swagger-ui-dist-3.23.11.tgz",
+      "integrity": "sha512-ipENHHH/sqpngTpHXUwg55eAOZ7b2UVayUwwuWPA6nQSPhjBVXX4zOPpNKUwQIFOl3oIwVvZF7mqoxH7pMgVzA=="
     }
   }
 }
diff --git a/rswag-ui/package.json b/rswag-ui/package.json
index 27dbc6c..fd299d1 100644
--- a/rswag-ui/package.json
+++ b/rswag-ui/package.json
@@ -3,6 +3,6 @@
   "version": "1.0.0",
   "private": true,
   "dependencies": {
-    "swagger-ui-dist": "3.18.2"
+    "swagger-ui-dist": "3.23.11"
   }
 }
diff --git a/test-app/db/schema.rb b/test-app/db/schema.rb
index 440d919..e01f8f3 100644
--- a/test-app/db/schema.rb
+++ b/test-app/db/schema.rb
@@ -2,11 +2,11 @@
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
 #
-# Note that this schema.rb definition is the authoritative source for your
-# database schema. If you need to create the application database on another
-# system, you should be using db:schema:load, not running all the migrations
-# from scratch. The latter is a flawed and unsustainable approach (the more migrations
-# you'll amass, the slower it'll run and the greater likelihood for issues).
+# This file is the source Rails uses to define your schema when running `rails
+# db:schema:load`. When creating a new database, `rails db:schema:load` tends to
+# be faster and is potentially less error prone than running all of your
+# migrations from scratch. Old migrations may fail to apply correctly if those
+# migrations use external dependencies or application code.
 #
 # It's strongly recommended that you check this file into your version control system.
 
diff --git a/test-app/spec/features/swagger_ui_spec.rb b/test-app/spec/features/swagger_ui_spec.rb
index 24d5790..484ad65 100644
--- a/test-app/spec/features/swagger_ui_spec.rb
+++ b/test-app/spec/features/swagger_ui_spec.rb
@@ -5,8 +5,8 @@ RSpec.feature 'swagger-ui', js: true do
   scenario 'browsing api-docs' do
     visit '/api-docs'
 
-    expect(page).to have_content('GET /blogs Searches blogs')
-    expect(page).to have_content('POST /blogs Creates a blog')
-    expect(page).to have_content('GET /blogs/{id} Retrieves a blog')
+    expect(page).to have_content('GET /blogs Searches blogs', normalize_ws: true)
+    expect(page).to have_content('POST /blogs Creates a blog', normalize_ws: true)
+    expect(page).to have_content('GET /blogs/{id} Retrieves a blog', normalize_ws: true)
   end
 end
diff --git a/test-app/spec/rails_helper.rb b/test-app/spec/rails_helper.rb
index d1bc219..7c64595 100644
--- a/test-app/spec/rails_helper.rb
+++ b/test-app/spec/rails_helper.rb
@@ -53,7 +53,15 @@ RSpec.configure do |config|
   # arbitrary gems may also be filtered via:
   # config.filter_gems_from_backtrace("gem name")
 
-  Capybara.javascript_driver = :webkit
+  Capybara.register_driver :firefox_headless do |app|
+    options = ::Selenium::WebDriver::Firefox::Options.new
+    options.args << '--headless'
+
+    Capybara::Selenium::Driver.new(app, browser: :firefox, options: options)
+  end
+
+  Capybara.javascript_driver = :firefox_headless
 end
 
 Capybara::Webkit.configure(&:block_unknown_urls)
+