diff --git a/content/README.md b/content/README.md
index 901427d4be71..71f39c6f2f34 100644
--- a/content/README.md
+++ b/content/README.md
@@ -20,6 +20,7 @@ See the [contributing docs](/CONTRIBUTING.md) for general information about work
   - [`showMiniToc`](#showminitoc)
   - [`miniTocMaxHeadingLevel`](#minitocmaxheadinglevel)
   - [`allowTitleToDifferFromFilename`](#allowtitletodifferfromfilename)
+  - [`defaultPlatform`](#defaultplatform)
   - [Escaping single quotes](#escaping-single-quotes)
 - [Autogenerated mini TOCs](#autogenerated-mini-tocs)
 - [Versioning](#versioning)
@@ -172,6 +173,18 @@ featuredLinks:
 - Type: `Array`, items are objects `{ href: string, title: string, date: 'YYYY-MM-DD' }`
 - Optional.
 
+### `defaultPlatform`
+
+- Purpose: Override the initial platform selection for a page. If this frontmatter is omitted, then the platform-specific content matching the reader's operating system is shown by default. This behavior can be changed for individual pages, for which a manual selection is more reasonable. For example, most GitHub Actions runners use Linux and their operating system is independent of the reader's operating system.
+- Type: `String`, one of: `mac`, `windows`, `linux`.
+- Optional.
+
+Example:
+
+```yaml
+defaultPlatform: linux
+```
+
 ### Escaping single quotes
 
 If you see two single quotes in a row (`''`) in YML frontmatter where you might expect to see one (`'`), this is the YML-preferred way to escape a single quote. From [the YAML spec](https://yaml.org/spec/history/2001-12-10.html):
diff --git a/contributing/content-markup-reference.md b/contributing/content-markup-reference.md
index f1705278da36..7e33130350a0 100644
--- a/contributing/content-markup-reference.md
+++ b/contributing/content-markup-reference.md
@@ -81,6 +81,7 @@ These instructions are pertinent to Mac users.
 
 {% endmac %}
 ```
+
 ```
 {% windows %}
 
@@ -88,6 +89,7 @@ These instructions are pertinent to Windows users.
 
 {% endwindows %}
 ```
+
 ```
 {% linux %}
 
@@ -96,15 +98,7 @@ These instructions are pertinent to Windows users.
 {% endlinux %}
 ```
 
-The platform-specific content matching the reader's operating system shows by default. You can override this behavior for individual Markdown files with the `defaultPlatform` frontmatter (such as for pages about GitHub Actions runners, which mostly use Linux):
-
-```
----
-title: …
-versions: …
-defaultPlatform: linux
----
-```
+You can define a default platform in the frontmatter, see the [content README](../content/README.md#defaultplatform).
 
 ## Reusable and variable strings of text