diff --git a/guides/source/action_text_overview.md b/guides/source/action_text_overview.md
index 2950a87d3b446..6d398ffa49231 100644
--- a/guides/source/action_text_overview.md
+++ b/guides/source/action_text_overview.md
@@ -65,7 +65,7 @@ After the installation is complete, a Rails app using Webpacker should have the
 
     Additionally, this `actiontext.scss` file should be imported into your stylesheet pack.
 
-    ```
+    ```scss
     // application.scss
     @import "./actiontext.scss";
     ```
diff --git a/guides/source/asset_pipeline.md b/guides/source/asset_pipeline.md
index f189b773d7dbb..b1914c1e8c3b5 100644
--- a/guides/source/asset_pipeline.md
+++ b/guides/source/asset_pipeline.md
@@ -898,7 +898,7 @@ You can also set this value through an [environment
 variable](https://en.wikipedia.org/wiki/Environment_variable) to make running a
 staging copy of your site easier:
 
-```
+```ruby
 config.action_controller.asset_host = ENV['CDN_HOST']
 ```
 
@@ -1013,7 +1013,7 @@ the cache will store the object before invalidating the cache. The `max-age`
 value is set to seconds with a maximum possible value of `31536000` which is one
 year. You can do this in your Rails application by setting
 
-```
+```ruby
 config.public_file_server.headers = {
   'Cache-Control' => 'public, max-age=31536000'
 }
diff --git a/guides/source/autoloading_and_reloading_constants.md b/guides/source/autoloading_and_reloading_constants.md
index 332f3b4eb3108..57c404b7e19d3 100644
--- a/guides/source/autoloading_and_reloading_constants.md
+++ b/guides/source/autoloading_and_reloading_constants.md
@@ -172,7 +172,7 @@ Let's see other situations that involve stale class or module objects.
 
 Check this Rails console session:
 
-```
+```ruby
 > joe = User.new
 > reload!
 > alice = User.new
@@ -198,7 +198,7 @@ Bottom line: **do not cache reloadable classes or modules**.
 
 Applications can safely autoload constants during boot using a reloader callback:
 
-```
+```ruby
 Rails.application.reloader.to_prepare do
   $PAYMENT_GATEWAY = Rails.env.production? ? RealGateway : MockedGateway
 end
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 34b941b182b11..cd43e9bd91859 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -1381,7 +1381,7 @@ You can find more information in the [Unicorn readme](https://bogomips.org/unico
 
 Once you've configured the application server, you must proxy requests to it by configuring your web server appropriately. For example your NGINX config may include:
 
-```
+```nginx
 upstream application_server {
   server 0.0.0.0:8080;
 }
diff --git a/guides/source/debugging_rails_applications.md b/guides/source/debugging_rails_applications.md
index d70a2893fc61b..04b6684595298 100644
--- a/guides/source/debugging_rails_applications.md
+++ b/guides/source/debugging_rails_applications.md
@@ -331,7 +331,7 @@ application server, and you will be placed at the debugger's prompt `(byebug)`.
 Before the prompt, the code around the line that is about to be run will be
 displayed and the current line will be marked by '=>', like this:
 
-```
+```ruby
 [1, 10] in /PathTo/project/app/controllers/articles_controller.rb
     3:
     4:   # GET /articles
diff --git a/guides/source/engines.md b/guides/source/engines.md
index c8313f1a5d264..bd1fc3b4a6518 100644
--- a/guides/source/engines.md
+++ b/guides/source/engines.md
@@ -1338,7 +1338,7 @@ were inside the engine:
 You can also specify these assets as dependencies of other assets using Asset
 Pipeline require statements in processed files:
 
-```
+```css
 /*
  *= require blorgh/style
 */
diff --git a/guides/source/generators.md b/guides/source/generators.md
index db6503b03df06..8368cd111f7b9 100644
--- a/guides/source/generators.md
+++ b/guides/source/generators.md
@@ -468,7 +468,7 @@ Adding Command Line Arguments
 -----------------------------
 Rails generators can be easily modified to accept custom command line arguments. This functionality comes from [Thor](https://www.rubydoc.info/github/erikhuda/thor/master/Thor/Base/ClassMethods#class_option-instance_method):
 
-```
+```ruby
 class_option :scope, type: :string, default: 'read_products'
 ```
 
diff --git a/guides/source/layouts_and_rendering.md b/guides/source/layouts_and_rendering.md
index 6ec5613e3fcab..62e8b9a73ad8b 100644
--- a/guides/source/layouts_and_rendering.md
+++ b/guides/source/layouts_and_rendering.md
@@ -754,7 +754,7 @@ head :bad_request
 
 This would produce the following header:
 
-```
+```http
 HTTP/1.1 400 Bad Request
 Connection: close
 Date: Sun, 24 Jan 2010 12:15:53 GMT
@@ -773,7 +773,7 @@ head :created, location: photo_path(@photo)
 
 Which would produce:
 
-```
+```http
 HTTP/1.1 201 Created
 Connection: close
 Date: Sun, 24 Jan 2010 12:16:44 GMT
diff --git a/guides/source/security.md b/guides/source/security.md
index 3a3bad270e4d7..9c9972b57d8e0 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -734,7 +734,7 @@ This JavaScript code will simply display an alert box. The next examples do exac
 
 These examples don't do any harm so far, so let's see how an attacker can steal the user's cookie (and thus hijack the user's session). In JavaScript you can use the `document.cookie` property to read and write the document's cookie. JavaScript enforces the same origin policy, that means a script from one domain cannot access cookies of another domain. The `document.cookie` property holds the cookie of the originating web server. However, you can read and write this property, if you embed the code directly in the HTML document (as it happens with XSS). Inject this anywhere in your web application to see your own cookie on the result page:
 
-```
+```html
 <script>document.write(document.cookie);</script>
 ```
 
@@ -798,7 +798,7 @@ As a second step, _it is good practice to escape all output of the application_,
 
 Network traffic is mostly based on the limited Western alphabet, so new character encodings, such as Unicode, emerged, to transmit characters in other languages. But, this is also a threat to web applications, as malicious code can be hidden in different encodings that the web browser might be able to process, but the web application might not. Here is an attack vector in UTF-8 encoding:
 
-```
+```html
 <IMG SRC=&#106;&#97;&#118;&#97;&#115;&#99;&#114;&#105;&#112;&#116;&#58;&#97;
   &#108;&#101;&#114;&#116;&#40;&#39;&#88;&#83;&#83;&#39;&#41;>
 ```
@@ -811,7 +811,7 @@ _In order to understand today's attacks on web applications, it's best to take a
 
 The following is an excerpt from the [Js.Yamanner@m](http://www.symantec.com/security_response/writeup.jsp?docid=2006-061211-4111-99&tabid=1) Yahoo! Mail [worm](http://groovin.net/stuff/yammer.txt). It appeared on June 11, 2006 and was the first webmail interface worm:
 
-```
+```html
 <img src='http://us.i1.yimg.com/us.yimg.com/i/us/nt/ma/ma_mail_1.gif'
   target=""onload="var http_request = false;    var Email = '';
   var IDList = '';   var CRumb = '';   function makeRequest(url, Func, Method,Param) { ...
@@ -843,7 +843,7 @@ So the payload is in the style attribute. But there are no quotes allowed in the
 
 The `eval()` function is a nightmare for restricted list input filters, as it allows the style attribute to hide the word "innerHTML":
 
-```
+```js
 alert(eval('document.body.inne' + 'rHTML'));
 ```
 
@@ -939,7 +939,7 @@ http://www.yourapplication.com/controller/action?referer=path/at/your/app%0d%0aL
 
 Note that `%0d%0a` is URL-encoded for `\r\n` which is a carriage-return and line-feed (CRLF) in Ruby. So the resulting HTTP header for the second example will be the following because the second Location header field overwrites the first.
 
-```
+```http
 HTTP/1.1 302 Moved Temporarily
 (...)
 Location: http://www.malicious.tld
@@ -951,7 +951,7 @@ So _attack vectors for Header Injection are based on the injection of CRLF chara
 
 If Header Injection was possible, Response Splitting might be, too. In HTTP, the header block is followed by two CRLFs and the actual data (usually HTML). The idea of Response Splitting is to inject two CRLFs into a header field, followed by another response with malicious HTML. The response will be:
 
-```
+```http
 HTTP/1.1 302 Found [First standard 302 response]
 Date: Tue, 12 Apr 2005 22:09:07 GMT
 Location:Content-Type: text/html
diff --git a/guides/source/upgrading_ruby_on_rails.md b/guides/source/upgrading_ruby_on_rails.md
index 2904ffd59dc9f..d02759569d14b 100644
--- a/guides/source/upgrading_ruby_on_rails.md
+++ b/guides/source/upgrading_ruby_on_rails.md
@@ -668,7 +668,7 @@ model behavior.
 When upgrading from Rails 4.2 to Rails 5.0, you need to create an
 `application_record.rb` file in `app/models/` and add the following content:
 
-```
+```ruby
 class ApplicationRecord < ActiveRecord::Base
   self.abstract_class = true
 end
@@ -709,7 +709,7 @@ behavior has changed to now inherit from `ApplicationJob`.
 When upgrading from Rails 4.2 to Rails 5.0, you need to create an
 `application_job.rb` file in `app/jobs/` and add the following content:
 
-```
+```ruby
 class ApplicationJob < ActiveJob::Base
 end
 ```
@@ -1383,7 +1383,7 @@ gem to your `Gemfile`.
 now returns millisecond precision by default. If you need to keep old behavior with no millisecond
 precision, set the following in an initializer:
 
-```
+```ruby
 ActiveSupport::JSON::Encoding.time_precision = 0
 ```
 
@@ -1674,7 +1674,7 @@ used with `PATCH`](http://www.rfc-editor.org/errata_search.php?rfc=5789). One
 such format is [JSON Patch](https://tools.ietf.org/html/rfc6902). While Rails
 does not support JSON Patch natively, it's easy enough to add support:
 
-```
+```ruby
 # in your controller
 def update
   respond_to do |format|
diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index c93ef6f25e4f4..3924e0c1c2d6b 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -4,8 +4,8 @@
 
     Usage:
 
-    ```
-    rails generate scaffold Pet name:string --database=animals
+    ```bash
+    $ bin/rails generate scaffold Pet name:string --database=animals
     ```
 
     Will create an abstract class for the animals connection.
@@ -27,8 +27,8 @@
 
     If you already have an abstract class and it follows a different pattern than Rails defaults, you can pass a parent class with the database argument.
 
-    ```
-    rails generate scaffold Pet name:string --database=animals --parent=SecondaryBase
+    ```bash
+    $ bin/rails generate scaffold Pet name:string --database=animals --parent=SecondaryBase
     ```
 
     This will ensure the model inherits from the `SecondaryBase` parent instead of `AnimalsRecord`
@@ -205,7 +205,7 @@
 
     Previously:
 
-    ```
+    ```bash
     $ bin/rails g migration add_location_to_users location:references
     ```