--- a/toolkit/components/telemetry/Scalars.yaml
+++ b/toolkit/components/telemetry/Scalars.yaml
@@ -1727,16 +1727,35 @@ browser.errors:
     expires: "64"
     kind: uint
     notification_emails:
       - nightly-js-errors@mozilla.com
       - mkelly@mozilla.com
     record_in_processes:
       - 'main'
 
+widget:
+  ime_name_on_windows:
+    bug_numbers:
+      - 1215818
+    description: >
+      Locale ID and name of IME which was selected by users on Windows.  This
+      does NOT collect legacy IMM-IME names since we cannot get readable names
+      and we do not support IMM-IME so aggressively because IME vendors
+      should've already released TIP for TSF for supporting Windows 8 or later
+      completely.
+    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/windows/TSFTextStore.cpp
+++ b/widget/windows/TSFTextStore.cpp
@@ -13,16 +13,17 @@
 
 #include "IMMHandler.h"
 #include "KeyboardLayout.h"
 #include "WinIMEHandler.h"
 #include "WinUtils.h"
 #include "mozilla/AutoRestore.h"
 #include "mozilla/Logging.h"
 #include "mozilla/Preferences.h"
+#include "mozilla/Telemetry.h"
 #include "mozilla/TextEventDispatcher.h"
 #include "mozilla/TextEvents.h"
 #include "mozilla/WindowsVersion.h"
 #include "nsIXULRuntime.h"
 #include "nsWindow.h"
 #include "nsPrintfCString.h"
 
 namespace mozilla {
@@ -1557,16 +1558,41 @@ TSFStaticSink::OnActivated(DWORD dwProfi
       (dwProfileType == TF_PROFILETYPE_KEYBOARDLAYOUT ||
        catid == GUID_TFCAT_TIP_KEYBOARD)) {
     mOnActivatedCalled = true;
     mActiveTIPGUID = guidProfile;
     mLangID = langid;
     mIsIMM_IME = IsIMM_IME(hkl);
     GetTIPDescription(rclsid, mLangID, guidProfile,
                       mActiveTIPKeyboardDescription);
+    if (mActiveTIPGUID != GUID_NULL) {
+      // key should be "LocaleID|Description".  Although GUID of the
+      // profile is unique key since description may be localized for system
+      // language, unfortunately, it's too long to record as key with its
+      // description.  Therefore, we should record only the description with
+      // LocaleID because Microsoft IME may not include language information.
+      // 72 is kMaximumKeyStringLength in TelemetryScalar.cpp
+      nsAutoString key;
+      key.AppendPrintf("0x%04X|", mLangID & 0xFFFF);
+      nsAutoString description(mActiveTIPKeyboardDescription);
+      static const uint32_t kMaxDescriptionLength = 72 - key.Length();
+      if (description.Length() > kMaxDescriptionLength) {
+        if (NS_IS_LOW_SURROGATE(description[kMaxDescriptionLength - 1]) &&
+            NS_IS_HIGH_SURROGATE(description[kMaxDescriptionLength - 2])) {
+          description.Truncate(kMaxDescriptionLength - 2);
+        } else {
+          description.Truncate(kMaxDescriptionLength - 1);
+        }
+        // U+2026 is "..."
+        description.Append(char16_t(0x2026));
+      }
+      key.Append(description);
+      Telemetry::ScalarSet(Telemetry::ScalarID::WIDGET_IME_NAME_ON_WINDOWS,
+                           key, true);
+    }
     // Notify IMEHandler of changing active keyboard layout.
     IMEHandler::OnKeyboardLayoutChanged();
   }
   MOZ_LOG(sTextStoreLog, LogLevel::Info,
     ("0x%p TSFStaticSink::OnActivated(dwProfileType=%s (0x%08X), "
      "langid=0x%08X, rclsid=%s, catid=%s, guidProfile=%s, hkl=0x%08X, "
      "dwFlags=0x%08X (TF_IPSINK_FLAG_ACTIVE: %s)), mIsIMM_IME=%s, "
      "mActiveTIPDescription=\"%s\"",