diff --git a/mobile/android/chrome/geckoview/GeckoViewContentChild.js b/mobile/android/chrome/geckoview/GeckoViewContentChild.js
index e3e8e5ee4a66..97fba76c743d 100644
--- a/mobile/android/chrome/geckoview/GeckoViewContentChild.js
+++ b/mobile/android/chrome/geckoview/GeckoViewContentChild.js
@@ -39,6 +39,8 @@ class GeckoViewContentChild extends GeckoViewChildModule {
     });
 
     this.timeoutsSuspended = false;
+    this.lastViewportFit = "";
+    this.triggerViewportFitChange = null;
 
     this.messageManager.addMessageListener(
       "GeckoView:DOMFullscreenEntered",
@@ -80,6 +82,7 @@ class GeckoViewContentChild extends GeckoViewChildModule {
     addEventListener("contextmenu", this, { capture: true });
     addEventListener("DOMContentLoaded", this, false);
     addEventListener("MozFirstContentfulPaint", this, false);
+    addEventListener("DOMMetaViewportFitChanged", this, false);
   }
 
   onDisable() {
@@ -94,6 +97,7 @@ class GeckoViewContentChild extends GeckoViewChildModule {
     removeEventListener("contextmenu", this, { capture: true });
     removeEventListener("DOMContentLoaded", this);
     removeEventListener("MozFirstContentfulPaint", this);
+    removeEventListener("DOMMetaViewportFitChanged", this);
   }
 
   toPixels(aLength, aType) {
@@ -124,6 +128,24 @@ class GeckoViewContentChild extends GeckoViewChildModule {
     return content.windowUtils.SCROLL_MODE_SMOOTH;
   }
 
+  notifyParentOfViewportFit() {
+    if (this.triggerViewportFitChange) {
+      content.cancelIdleCallback(this.triggerViewportFitChange);
+    }
+    this.triggerViewportFitChange = content.requestIdleCallback(() => {
+      this.triggerViewportFitChange = null;
+      let viewportFit = content.windowUtils.getViewportFitInfo();
+      if (this.lastViewportFit === viewportFit) {
+        return;
+      }
+      this.lastViewportFit = viewportFit;
+      this.eventDispatcher.sendRequest({
+        type: "GeckoView:DOMMetaViewportFit",
+        viewportfit: viewportFit,
+      });
+    });
+  }
+
   receiveMessage(aMsg) {
     debug`receiveMessage: ${aMsg.name}`;
 
@@ -271,6 +293,11 @@ class GeckoViewContentChild extends GeckoViewChildModule {
             content.windowUtils.resumeTimeouts();
             this.timeoutsSuspended = false;
           }
+          if (aMsg.data.active) {
+            // Send current viewport-fit to parent.
+            this.lastViewportFit = "";
+            this.notifyParentOfViewportFit();
+          }
         }
         if (content && aMsg.data.suspendMedia) {
           content.windowUtils.mediaSuspend = aMsg.data.active
@@ -380,6 +407,11 @@ class GeckoViewContentChild extends GeckoViewChildModule {
       case "MozDOMFullscreen:Exit":
         sendAsyncMessage("GeckoView:DOMFullscreenExit");
         break;
+      case "DOMMetaViewportFitChanged":
+        if (aEvent.originalTarget.ownerGlobal == content) {
+          this.notifyParentOfViewportFit();
+        }
+        break;
       case "DOMTitleChanged":
         this.eventDispatcher.sendRequest({
           type: "GeckoView:DOMTitleChanged",
@@ -408,6 +440,11 @@ class GeckoViewContentChild extends GeckoViewChildModule {
         }
         break;
       case "DOMContentLoaded": {
+        if (aEvent.originalTarget.ownerGlobal == content) {
+          // If loaded content doesn't have viewport-fit, parent still
+          // uses old value of previous content.
+          this.notifyParentOfViewportFit();
+        }
         content.requestIdleCallback(async () => {
           const manifest = await ManifestObtainer.contentObtainManifest(
             content
diff --git a/mobile/android/geckoview/api.txt b/mobile/android/geckoview/api.txt
index 91446fcad8d6..be2626e2ed76 100644
--- a/mobile/android/geckoview/api.txt
+++ b/mobile/android/geckoview/api.txt
@@ -687,6 +687,7 @@ package org.mozilla.geckoview {
     method @UiThread default public void onFocusRequest(@NonNull GeckoSession);
     method @UiThread default public void onFullScreen(@NonNull GeckoSession, boolean);
     method @UiThread default public void onKill(@NonNull GeckoSession);
+    method @UiThread default public void onMetaViewportFitChange(@NonNull GeckoSession, @NonNull String);
     method @UiThread @Nullable default public GeckoResult<SlowScriptResponse> onSlowScript(@NonNull GeckoSession, @NonNull String);
     method @UiThread default public void onTitleChange(@NonNull GeckoSession, @Nullable String);
     method @UiThread default public void onWebAppManifest(@NonNull GeckoSession, @NonNull JSONObject);
diff --git a/mobile/android/geckoview/src/androidTest/assets/www/viewport.html b/mobile/android/geckoview/src/androidTest/assets/www/viewport.html
index d55b4a0ee9c3..9594246ed954 100644
--- a/mobile/android/geckoview/src/androidTest/assets/www/viewport.html
+++ b/mobile/android/geckoview/src/androidTest/assets/www/viewport.html
@@ -1,7 +1,7 @@
 <html>
 <head>
 <meta charset="utf-8">
-<meta name="viewport" content="width=device-width, initial-scale=1.0">
+<meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover">
 <style type="text/css">
 #wide {
    background-color: rgb(200, 0, 0);
diff --git a/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/ContentDelegateTest.kt b/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/ContentDelegateTest.kt
index 6d17e5dd5248..ce7c78d32ca5 100644
--- a/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/ContentDelegateTest.kt
+++ b/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/ContentDelegateTest.kt
@@ -327,6 +327,33 @@ class ContentDelegateTest : BaseSessionTest() {
         })
     }
 
+    @Test fun viewportFit() {
+        mainSession.loadTestPath(VIEWPORT_PATH)
+        mainSession.waitUntilCalled(object : Callbacks.All {
+            @AssertCalled(count = 1)
+            override fun onPageStop(session: GeckoSession, success: Boolean) {
+                assertThat("Page load should succeed", success, equalTo(true))
+            }
+
+            @AssertCalled(count = 1)
+            override fun onMetaViewportFitChange(session: GeckoSession, viewportFit: String) {
+                assertThat("viewport-fit should match", viewportFit, equalTo("cover"))
+            }
+        })
+
+        mainSession.loadTestPath(HELLO_HTML_PATH)
+        mainSession.waitUntilCalled(object : Callbacks.All {
+            @AssertCalled(count = 1)
+            override fun onPageStop(session: GeckoSession, success: Boolean) {
+                assertThat("Page load should succeed", success, equalTo(true))
+            }
+
+            @AssertCalled(count = 1)
+            override fun onMetaViewportFitChange(session: GeckoSession, viewportFit: String) {
+                assertThat("viewport-fit should match", viewportFit, equalTo("auto"))
+            }
+        })
+    }
 
     /**
      * Preferences to induce wanted behaviour.
diff --git a/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoSession.java b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoSession.java
index 4bc77e659fe7..f8bcd0604fa4 100644
--- a/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoSession.java
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/GeckoSession.java
@@ -423,6 +423,7 @@ public class GeckoSession implements Parcelable {
                 "GeckoView:ContentCrash",
                 "GeckoView:ContentKill",
                 "GeckoView:ContextMenu",
+                "GeckoView:DOMMetaViewportFit",
                 "GeckoView:DOMTitleChanged",
                 "GeckoView:DOMWindowClose",
                 "GeckoView:ExternalResponse",
@@ -459,6 +460,9 @@ public class GeckoSession implements Parcelable {
                                            message.getInt("screenY"),
                                            elem);
 
+                } else if ("GeckoView:DOMMetaViewportFit".equals(event)) {
+                    delegate.onMetaViewportFitChange(GeckoSession.this,
+                                                     message.getString("viewportfit"));
                 } else if ("GeckoView:DOMTitleChanged".equals(event)) {
                     delegate.onTitleChange(GeckoSession.this,
                                            message.getString("title"));
@@ -3014,6 +3018,16 @@ public class GeckoSession implements Parcelable {
         @UiThread
         default void onFullScreen(@NonNull GeckoSession session, boolean fullScreen) {}
 
+        /**
+         * A viewport-fit was discovered in the content or updated after the content.
+         *
+         * @param session The GeckoSession that initiated the callback.
+         * @param viewportFit The value of viewport-fit of meta element in content.
+         * @see <a href="https://drafts.csswg.org/css-round-display/#viewport-fit-descriptor">4.1. The viewport-fit descriptor</a>
+         */
+        @UiThread
+        default void onMetaViewportFitChange(@NonNull GeckoSession session, @NonNull String viewportFit) {}
+
         /**
          * Element details for onContextMenu callbacks.
          */
diff --git a/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md
index c324a75c3826..1bdd8925323b 100644
--- a/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md
+++ b/mobile/android/geckoview/src/main/java/org/mozilla/geckoview/doc-files/CHANGELOG.md
@@ -33,6 +33,7 @@ exclude: true
   exceptions and to add better support for removing exceptions. This deprecates [`ExceptionList`][74.8]
   and [`restoreExceptionList`][74.9] with the intent to remove them in 76.
   ([bug 1587552]({{bugzilla}}1587552))
+- Added [`GeckoSession.ContentDelegate.onMetaViewportFitChange`][74.10]. This exposes `viewport-fit` value that is CSS Round Display Level 1. ([bug 1574307]({{bugzilla}}1574307))
 
 [74.1]: {{javadoc_uri}}/WebExtensionController.html#enable-org.mozilla.geckoview.WebExtension-int-
 [74.2]: {{javadoc_uri}}/WebExtensionController.html#disable-org.mozilla.geckoview.WebExtension-int-
@@ -43,6 +44,7 @@ exclude: true
 [74.7]: {{javadoc_uri}}/ContentBlockingController.html
 [74.8]: {{javadoc_uri}}/ContentBlockingController.ExceptionList.html
 [74.9]: {{javadoc_uri}}/ContentBlockingController.html#restoreExceptionList-org.mozilla.geckoview.ContentBlockingController.ExceptionList-
+[74.10]: {{javadoc_uri}}/GeckoSession.ContentDelegate.html#onMetaViewportFitChange-org.mozilla.geckoview.GeckoSession-java.lang.String-
 
 ## v73
 - Added [`WebExtensionController.install`][73.1] and [`uninstall`][73.2] to
@@ -553,4 +555,4 @@ exclude: true
 [65.24]: {{javadoc_uri}}/CrashReporter.html#sendCrashReport-android.content.Context-android.os.Bundle-java.lang.String-
 [65.25]: {{javadoc_uri}}/GeckoResult.html
 
-[api-version]: e89f3bb79d0c5cc936812de4c2d8f4d30923afb9
+[api-version]: 5342560e4c467a1f3d363748ebb20a077d2e8385