3 files changed, 39 insertions, 6 deletions
diff --git a/guides/source/active_storage_overview.md b/guides/source/active_storage_overview.md
index cb9acdadcf..e7a94fc510 100644
--- a/guides/source/active_storage_overview.md
+++ b/guides/source/active_storage_overview.md
@@ -446,11 +446,12 @@ the box, Active Storage supports previewing videos and PDF documents.
 </ul>
 ```
 
-WARNING: Extracting previews requires third-party applications, `ffmpeg` for
-video and `mutool` for PDFs. These libraries are not provided by Rails. You must
-install them yourself to use the built-in previewers. Before you install and use
-third-party software, make sure you understand the licensing implications of
-doing so.
+WARNING: Extracting previews requires third-party applications, `FFmpeg` for
+video and `muPDF` for PDFs, and on macOS also `XQuartz` and `Poppler`.
+These libraries are not provided by Rails. You must install them yourself to
+use the built-in previewers. Before you install and use third-party software,
+make sure you understand the licensing implications of doing so.
+
 
 Direct Uploads
 --------------
diff --git a/guides/source/configuring.md b/guides/source/configuring.md
index 4d8883a7bd..4c2dea6721 100644
--- a/guides/source/configuring.md
+++ b/guides/source/configuring.md
@@ -305,6 +305,10 @@ All these configuration options are delegated to the `I18n` library.
     config.i18n.fallbacks.map = { az: :tr, da: [:de, :en] }
     ```
 
+### Configuring Active Model
+
+* `config.active_model.i18n_full_message` is a boolean value which controls whether the `full_message` error format can be overridden at the attribute or model level in the locale files
+
 ### Configuring Active Record
 
 `config.active_record` includes a variety of configuration options:
@@ -793,7 +797,7 @@ normal Rails server.
    config.active_storage.paths[:ffprobe] = '/usr/local/bin/ffprobe'
    ```
 
-* `config.active_storage.variable_content_types` accepts an array of strings indicating the content types that Active Storage can transform through ImageMagick. The default is `%w(image/png image/gif image/jpg image/jpeg image/vnd.adobe.photoshop)`.
+* `config.active_storage.variable_content_types` accepts an array of strings indicating the content types that Active Storage can transform through ImageMagick. The default is `%w(image/png image/gif image/jpg image/jpeg image/vnd.adobe.photoshop image/vnd.microsoft.icon)`.
 
 * `config.active_storage.content_types_to_serve_as_binary` accepts an array of strings indicating the content types that Active Storage will always serve as an attachment, rather than inline. The default is `%w(text/html
 text/javascript image/svg+xml application/postscript application/x-shockwave-flash text/xml application/xml application/xhtml+xml)`.
diff --git a/guides/source/development_dependencies_install.md b/guides/source/development_dependencies_install.md
index 50274d700b..fdd560ccf3 100644
--- a/guides/source/development_dependencies_install.md
+++ b/guides/source/development_dependencies_install.md
@@ -376,3 +376,31 @@ command inside of the `activestorage` directory to install the dependencies:
 ```bash
 yarn install
 ```
+
+Extracting previews, tested in ActiveStorage's test suite requires third-party
+applications, `FFmpeg` for video and `muPDF` for PDFs, and on macOS also
+`XQuartz` and `Poppler`.. Without these applications installed, ActiveStorage
+tests will raise errors.
+
+On macOS you can run:
+
+```bash
+brew install ffmpeg
+brew cask install xquartz
+brew install mupdf-tools
+brew install poppler
+```
+
+On Ubuntu, you can run:
+
+```bash
+sudo apt-get update && install ffmpeg
+sudo apt-get update && install mupdf mupdf-tools
+```
+
+On Fedora or CentOS, just run:
+
+```bash
+sudo yum install ffmpeg
+sudo yum install mupdf
+```