diff --git a/src/_help/specification-support/extensions.md b/src/_help/specification-support/extensions.md
index bc47c008..bf9ef25b 100644
--- a/src/_help/specification-support/extensions.md
+++ b/src/_help/specification-support/extensions.md
@@ -24,6 +24,46 @@ This custom property allows you to identify some components of your
 documentation as beta. Find out more in our [dedicated
 section](/help/specification-support/doc-beta).
 
+## Give precision to the state of your features (`x-state`) 
+
+This custom property can be added inside an operation or a property to identify it with a custom tag.
+The `x-state` property is a string.
+
+### Example usage
+
+Here under is an example of an operation and a property with a `x-state`.
+
+```yaml
+paths:
+  /diffs:
+    post:
+      tags: ["x-state"]
+      description: Create a diff between any two given API definitions
+      x-state: Technical preview # x-state flag at the operation level
+      requestBody:
+        description: The diff creation request object
+        content:
+          application/json:
+            schema:
+              type: object
+              properties:
+                url:
+                  type: string
+                  format: uri
+                  x-state: Still unstable # x-state flag at the object property level
+                  description: |
+                    **Required** if `definition` is not present.
+                    Current definition URL. It should be accessible through HTTP by Bump.sh servers.
+```
+
+Adding or removing this property is a structural change.
+When combined with the `x-beta`, the `x-state` replaces its value, but keeps the beta behavior: a change in a beta component is never identified as a breaking change.
+
+The documentation displays custom tags on the operation and property:
+
+![doc-beta.png](/images/help/doc-x-state.png)
+
+
 ## Get feedback from users (`x-feedbackLink`)
 
 This custom property allows you to add a button to your documentation that enables you to collect feedback from your users. Find out more in our [dedicated
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