--- a/toolkit/components/telemetry/Scalars.yaml
+++ b/toolkit/components/telemetry/Scalars.yaml
@@ -1763,16 +1763,33 @@ widget:
     expires: never
     kind: boolean
     notification_emails:
       - mnakano@mozilla.com
     release_channel_collection: opt-out
     record_in_processes:
       - 'main'
 
+  ime_name_on_linux:
+    bug_numbers:
+      - 1215818
+    description: >
+      Name of active IM (e.g., xim, fcitx, ibus, etc) which was actually set by
+      env on Linux.  Different from Windows and macOS, this value includes
+      non-IME users even though this is recoded when first compositionstart
+      event because dead key is also implemented by IME on Linux.
+    keyed: true
+    expires: never
+    kind: boolean
+    notification_emails:
+      - mnakano@mozilla.com
+    release_channel_collection: opt-out
+    record_in_processes:
+      - 'main'
+
 # The following section contains memory reporter counters.
 memoryreporter:
   max_ghost_windows:
     bug_numbers:
       - 1454724
     description: >
       The maximum number of leaked ghost windows seen.
     expires: "66"

--- a/widget/gtk/IMContextWrapper.cpp
+++ b/widget/gtk/IMContextWrapper.cpp
@@ -9,16 +9,17 @@
 
 #include "IMContextWrapper.h"
 #include "nsGtkKeyUtils.h"
 #include "nsWindow.h"
 #include "mozilla/AutoRestore.h"
 #include "mozilla/Likely.h"
 #include "mozilla/MiscEvents.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/Telemetry.h"
 #include "mozilla/TextEventDispatcher.h"
 #include "mozilla/TextEvents.h"
 #include "WritingModes.h"
 
 namespace mozilla {
 namespace widget {
 
 LazyLogModule gGtkIMLog("nsGtkIMModuleWidgets");
@@ -1971,16 +1972,24 @@ IMContextWrapper::DispatchCompositionSta
     if (NS_WARN_IF(NS_FAILED(rv))) {
         MOZ_LOG(gGtkIMLog, LogLevel::Error,
             ("0x%p   DispatchCompositionStart(), FAILED, "
              "due to BeginNativeInputTransaction() failure",
              this));
         return false;
     }
 
+    static bool sHasSetTelemetry = false;
+    if (!sHasSetTelemetry) {
+        sHasSetTelemetry = true;
+        NS_ConvertUTF8toUTF16 im(GetIMContextName(mIMContextID));
+        Telemetry::ScalarSet(Telemetry::ScalarID::WIDGET_IME_NAME_ON_LINUX,
+                             im, true);
+    }
+
     MOZ_LOG(gGtkIMLog, LogLevel::Debug,
         ("0x%p   DispatchCompositionStart(), dispatching "
          "compositionstart... (mCompositionStart=%u)",
          this, mCompositionStart));
     mCompositionState = eCompositionState_CompositionStartDispatched;
     nsEventStatus status;
     dispatcher->StartComposition(status);
     if (lastFocusedWindow->IsDestroyed() ||

--- a/widget/gtk/IMContextWrapper.h
+++ b/widget/gtk/IMContextWrapper.h
@@ -123,16 +123,34 @@ public:
                 return "eScim";
             case IMContextID::eUim:
                 return "eUim";
             default:
                 return "eUnknown";
         }
     }
 
+    static const char* GetIMContextName(IMContextID aIMContextID)
+    {
+        switch (aIMContextID) {
+            case IMContextID::eFcitx:
+                return "fcitx";
+            case IMContextID::eIBus:
+                return "ibus";
+            case IMContextID::eIIIMF:
+                return "iiim";
+            case IMContextID::eScim:
+                return "scim";
+            case IMContextID::eUim:
+                return "uim";
+            default:
+                return "<unknown>";
+        }
+    }
+
 protected:
     ~IMContextWrapper();
 
     // Owner of an instance of this class. This should be top level window.
     // The owner window must release the contexts when it's destroyed because
     // the IME contexts need the native window.  If OnDestroyWindow() is called
     // with the owner window, it'll release IME contexts.  Otherwise, it'll
     // just clean up any existing composition if it's related to the destroying