Why Japanese IME Stops Switching Modes and How to Fix It on Windows 11

Quick fix: Restart the IME with ctfmon.exe from the Run box, or remove and re-add Japanese under Settings → Time & language → Language & region. The 24H2 IME has a known bug where the half-width/full-width state desynchronizes after sleep, and a service restart clears it.

Japanese IME on Windows 11 is supposed to switch between hiragana, katakana, half-width English, and full-width English using the Alt+~ key (or the dedicated 半角/全角 key on Japanese keyboards). When it stops responding, the keyboard becomes useless for Japanese input — every keystroke goes through as half-width Latin even though the IME indicator says it’s in Japanese mode. The cause is usually a stuck Text Services Framework process, not a corrupted language pack.

What causes this

The Japanese IME runs as a Text Services Framework (TSF) input processor managed by ctfmon.exe. When the system wakes from sleep, when an app crashes mid-composition, or when a Windows Update touches the language pack files, the ctfmon process can lose track of which IME state is active. The IME indicator shows one state, the input is interpreted as another, and the mode key stops working because the framework doesn’t know which IME instance to send it to.

Most fixes either restart ctfmon (cheap, takes seconds) or re-register the Japanese IME (slower, but resets all state). Reinstalling the language pack is overkill except after a Windows feature update broke the IME files.

Method 1: Restart ctfmon

1. Press Ctrl + Shift + Esc to open Task Manager.
2. Click the Details tab.
3. Find ctfmon.exe. Right-click and choose End task.
4. Press Win + R, type ctfmon.exe, press Enter to restart it. The IME indicator in the taskbar should refresh.
5. Open Notepad and test typing Japanese with Alt+~ to confirm switching works.

This resolves about 80% of stuck-IME cases. If it works once but the IME stops switching again the next day, you’ve confirmed the cause is sleep/wake timing — see Method 3.

Method 2: Remove and re-add Japanese as a language

When ctfmon restart doesn’t resolve it, the IME registration itself is corrupted. Re-adding Japanese forces a clean re-registration.

1. Open Settings → Time & language → Language & region.
2. Click the three-dot menu next to 日本語 and choose Remove. Confirm.
3. If Japanese was your only language, add another language first (English will already be there).
4. Click Add a language, search for Japanese, and add it. Check Language pack and Basic typing in the install options.
5. Wait for the install (~2 minutes). Sign out and back in.
6. Test the IME with Alt+~ or 半角/全角 in Notepad.

The re-add wipes any corrupted IME dictionaries and registers fresh. Your custom learned words and shortcuts will be lost — export them first via Microsoft IME → Settings → Dictionary tool → Export if you care.

Method 3: Stop ctfmon from being killed on sleep

If the issue recurs after every sleep cycle, the root cause is Windows aggressively killing background processes on Modern Standby. Disable that for ctfmon.

1. Open Task Scheduler. Navigate to Task Scheduler Library → Microsoft → Windows → TextServicesFramework.
2. Find MsCtfMonitor. Right-click and choose Properties.
3. On the Triggers tab, add a new trigger: At log on, any user, no delay.
4. On the Settings tab, check If the task fails, restart every 1 minute, up to 3 attempts.
5. Save and close. Test by putting the PC to sleep for a few minutes, waking, and trying the IME.

This ensures ctfmon restarts automatically if it gets killed during sleep, so you don’t have to fix it manually each morning.

How to verify the fix worked

• Open Notepad. Press Alt+~ (or 半角/全角). The IME indicator switches between “A” (half-width English) and “あ” (hiragana).
• Type a hiragana sequence and press Space to convert. Conversion candidates appear normally.
• Sleep the PC for 5 minutes, wake it, and try again. IME still responds.

If none of these work

If the IME still doesn’t respond after all three methods, check whether a non-Microsoft IME (Google IME, ATOK) is installed and competing for the TSF slot — disable or uninstall it via Settings → Apps → Installed apps. Also run sfc /scannow from an elevated Command Prompt to check for corrupted system files that affect TextServicesFramework. As a last resort, run dism /online /add-package /packagepath:C:\Windows\WinSxS with the Japanese language pack package name to force a system-level reinstall — in practice, an in-place repair upgrade is faster than tracking the right package.

Bottom line: Stuck Japanese IME is almost always a ctfmon hang. Restarting it fixes 80% of cases; re-adding Japanese fixes the rest. If it keeps coming back after sleep, the MsCtfMonitor task trigger is your permanent fix.