How to Fix Japanese Input Not Working on Ubuntu: Complete Guide to Mozc, Fcitx, and IME Settings

1. Introduction

When using Ubuntu, you may encounter issues such as “Japanese input does not work” or “Keyboard switching does not respond.” This often happens right after a fresh Ubuntu installation or after a system update.

This article explains how to identify the causes of Japanese input not working on Ubuntu and how to reliably enable Japanese input. Even beginners can follow the steps easily, as the procedures are explained in detail.

1.1 What Causes Japanese Input to Stop Working?

To use Japanese input on Ubuntu, you need software called an IME (Input Method Editor). While Windows uses tools such as “Microsoft IME” or “Google Japanese Input,” Ubuntu primarily uses Mozc or Fcitx.

However, Japanese input may not work due to the following reasons:

• The Japanese input system (IME) is not installed
• The IME is not configured correctly (Mozc or Fcitx is not applied)
• The keyboard switching settings are incorrect
• Settings were reset after an Ubuntu version upgrade
• Japanese input is disabled only in certain apps (e.g., Chrome, VS Code)

This article walks you through troubleshooting each of these problems to restore smooth Japanese input.

1.2 What You Will Be Able to Do After Reading This Guide

After reading this article, you will be able to:

• Enable Japanese input on Ubuntu with certainty
• Properly configure Mozc or Fcitx for comfortable Japanese typing
• Troubleshoot issues when Japanese input stops working
• Use keyboard shortcuts to switch input methods efficiently

This guide is written so beginners can follow simple steps without requiring advanced knowledge. Just proceed in order.

2. Identifying the Cause of Japanese Input Issues

There are several reasons why Japanese input may fail on Ubuntu. These can be categorized into four main causes:

1. The Japanese input system (IME) is not installed
2. The IME is not configured correctly
3. Keyboard settings are incorrect
4. Japanese input works in some apps but not others

Let’s examine each cause in more detail to identify where the issue lies.

2.1 IME (Japanese Input System) Is Not Installed

To use Japanese input on Ubuntu, an IME must be installed. In most environments, the Japanese input method used is Mozc, developed by Google.

How to Check

Run the following command to verify whether Mozc is installed:

dpkg -l | grep mozc

Example results:

• If you see ii ibus-mozc ... → Mozc is installed
• If nothing appears → Mozc is not installed and must be installed later

If Mozc is not installed, installation steps are provided in a later section.

2.2 IME Is Not Configured Correctly

Even if the IME is installed, Japanese input will not work unless it is configured properly. Ubuntu usually uses IBus as the input method framework that manages IMEs.

Check Current IME Settings

Run the following command to list available input engines:

ibus list-engine

Example results:

• If mozc appears → Mozc is configured
• If only xkb:us::eng appears → Mozc may not be applied

If IME settings are incorrect, we will fix it in the next section.

2.3 Incorrect Keyboard Settings

If your keyboard layout is not configured properly, switching to Japanese input may fail.

Check Current Keyboard Layout

Run the following command:

setxkbmap -query

Example result:

layout: jp

This means a Japanese (JIS) keyboard is configured.

layout: us

This means a US keyboard is configured.
If you are using a Japanese keyboard but “us” is set, input may not behave correctly and must be fixed later.

2.4 Japanese Input Does Not Work in Specific Applications

If Japanese input fails only in specific apps (Chrome, VS Code, LibreOffice), those apps may be causing the issue.

How to Check

• Test Japanese input in another app (e.g., Text Editor, Terminal)
• Chrome may allow input in the address bar but not on websites

Solutions for these cases appear later in the troubleshooting section.

3. How to Configure the Japanese Input System

Now that we’ve identified the possible causes, let’s walk through the steps to enable Japanese input in Ubuntu.

The main steps are:

1. Install Mozc (Japanese IME)
2. Add Mozc to Input Sources
3. Configure the input method and verify it works

Follow these steps in order to fix Japanese input reliably.

3.1 Install Mozc

Ubuntu’s default Japanese IME is “Mozc.” If it is not installed, install it with the steps below.

1. Update the System

First update your package list and system:

sudo apt update && sudo apt upgrade -y

2. Install Mozc

Then install Mozc:

sudo apt install ibus-mozc -y

3. Verify Mozc Installation

Check installation with:

dpkg -l | grep mozc

Example output:

ii  ibus-mozc   2.23.2815.102-1  amd64  Mozc engine for IBus

If you see similar output, Mozc is successfully installed.

3.2 Add Mozc to Input Sources

Once Mozc is installed, add it to Ubuntu’s input sources.

1. Add Input Source from Settings

1. Open Settings
2. Select Region & Language
3. Click “+” (Add) under Input Sources
4. Select Japanese (Mozc) and add it
5. Move Mozc to the top to prioritize it

2. Confirm Mozc Setup via Terminal

Check if Mozc is recognized as an input engine:

ibus list-engine

Expected Output:

mozc

If displayed, Mozc is active.

3. Restart IBus

Restart IBus to apply changes:

ibus restart

3.3 How to Switch Japanese Input

After adding Mozc, verify how to switch Japanese input modes.

1. Keyboard Shortcuts for Switching IME

Default keybindings:

• Hankaku/Zenkaku key (Japanese keyboard)
• Ctrl + Space (US keyboard)

If the “Hankaku/Zenkaku” key does not switch IME, change shortcut settings.

2. Change Input Method Shortcut

1. Open Settings
2. Select Keyboard Shortcuts
3. Search “Switch Input Method”
4. Assign a preferred shortcut (e.g., “Super + Space”)

3.4 Verify IME Activation

Check that IME is functioning properly.

1. Verify IME in Terminal

ibus engine

Expected Output:

mozc

If displayed, Mozc is functioning.

2. Test Japanese Input in a Text Editor

• Test in “Text Editor (Gedit)” or Terminal
• If you can type “あいうえお,” it is working correctly

4. Japanese Input Systems Other Than Mozc

While Mozc is the recommended default for Ubuntu, you may choose other IMEs such as Fcitx or Anthy depending on your environment.

Examples of when alternatives might be useful:

• Fcitx provides lighter and faster performance than IBus + Mozc
• Anthy works even in environments where Mozc cannot be used
• Useful as a workaround if Mozc fails in some applications

This section explains each IME and how to install them.

4.1 Using Fcitx + Mozc

What is Fcitx?

Fcitx (Flexible Input Method Framework) is a lightweight IME framework that often runs faster than IBus, especially on lower-spec PCs.

How to Install Fcitx

1. Install Fcitx and Mozc:

sudo apt update
sudo apt install fcitx fcitx-mozc -y

2. Set Fcitx as the default input framework:

im-config -n fcitx

3. Reboot or relogin to apply settings:

reboot

4. Verify activation:

echo $XMODIFIERS

Example Output:

@im=fcitx

If displayed, Fcitx is active.

Configure Fcitx via GUI

1. Open Fcitx Configuration Tool (fcitx-config-gtk3)
2. In the Input Method tab, add Mozc
3. Move Mozc to the top priority
4. Restart Fcitx

fcitx restart

Now Fcitx + Mozc is fully set up.

4.2 Using Anthy

What is Anthy?

Anthy is an alternative Japanese input engine. While less accurate than Mozc, it is useful in environments where Mozc cannot be installed.

How to Install Anthy

1. Install Anthy:

sudo apt install ibus-anthy -y

2. Add Japanese (Anthy) from Settings → Region & Language → Input Sources
3. Restart IBus:

ibus restart

4. Switch IME to verify operation

Anthy is lightweight but lower in accuracy, useful mainly for minimal environments.

4.3 Comparison: Mozc, Fcitx, and Anthy

5. Troubleshooting (Solutions)

Even with the correct settings, Japanese input may still fail. Try the following troubleshooting steps.

5.1 Mozc Does Not Input Japanese

If Mozc does not work even after installation and configuration, check the following:

1. Check Whether Mozc Is Installed

dpkg -l | grep mozc

If not installed, reinstall:

sudo apt install --reinstall ibus-mozc -y

2. Check Whether Mozc Is Active

ibus engine

Expected Output:

mozc

If not, activate manually:

ibus engine mozc

3. Restart Input Method

ibus restart

Rebooting the PC may also help.

5.2 Japanese Input Not Working in Specific Applications (Chrome, VS Code, etc.)

If Japanese input works in some apps but not others, try the following solutions.

1. If Japanese Input Does Not Work in Google Chrome

Chrome may fail to handle IME properly on certain web pages.

• You can input in the address bar but not within web pages
• Solution: Disable Hardware Acceleration

1. Enter chrome://settings/ in the address bar
2. Open “Advanced Settings” → “System”
3. Turn off “Use hardware acceleration when available”
4. Restart Chrome

2. If Japanese Input Fails in VS Code

Certain accessibility settings may cause IME not to work.

• Solution: Change Accessibility Settings

1. Press Ctrl + Shift + P to open the Command Palette
2. Search Preferences: Configure Language Specific Settings...
3. Set editor.accessibilitySupport to off
4. Restart VS Code

5.3 Japanese Conversion Is Slow or Lagging

If Japanese typing feels slow, adjusting Mozc settings can improve performance.

1. Open Mozc Settings

ibus-setup

Recommended performance tweaks:

• Disable “Suggestions (Predictive Conversion)”
• Disable “Dictionary Learning”
• Reduce the number of candidates displayed to around 5

These changes lighten Mozc’s processing and improve responsiveness.

5.4 Japanese Input Stops Working After Ubuntu Version Upgrade

Upgrading Ubuntu may reset IME-related settings.

1. Reset IBus Settings

dconf reset -f /desktop/ibus/
ibus restart

2. Reinstall Mozc

sudo apt install --reinstall ibus-mozc -y

3. Check Environment Variables

Run the following to verify IME settings:

echo $GTK_IM_MODULE
echo $QT_IM_MODULE
echo $XMODIFIERS

Expected Output:

GTK_IM_MODULE=ibus
QT_IM_MODULE=ibus
XMODIFIERS=@im=ibus

If incorrectly set, fix them:

export GTK_IM_MODULE=ibus
export QT_IM_MODULE=ibus
export XMODIFIERS=@im=ibus
ibus restart

5.5 Japanese Input Suddenly Stops Working

If Japanese input suddenly becomes unavailable, restarting IME often resolves it.

1. Restart IBus

ibus restart

2. Manually Enable Mozc

ibus engine mozc

3. Restart PC

Temporary issues may be resolved by rebooting.

6. FAQ (Frequently Asked Questions)

This section answers common questions regarding Japanese input not working or behaving inconsistently on Ubuntu. If previous steps did not solve your issue, refer to this FAQ.

Q1. What should I do if Japanese input suddenly stops working?

A:
First, try restarting IBus:

ibus restart

If it still doesn’t work, reapply the Mozc engine:

ibus engine mozc

Reinstalling Mozc can also help:

sudo apt install --reinstall ibus-mozc

Q2. How can I change the Japanese input switching key?

A:
You can change IME switching keys as follows:

1. Open “Settings” → “Keyboard Shortcuts”
2. Find “Switch input method” or “Select next input source”
3. Assign your preferred key combination (e.g., Super + Space, Ctrl + Shift)

Q3. Japanese input does not work in Chrome only. Why?

A:
This is usually caused by hardware acceleration.

Solution:

1. Enter chrome://settings/
2. Go to “Advanced Settings” → “System”
3. Disable “Use hardware acceleration when available”
4. Restart Chrome

Q4. Can I use Japanese input in Ubuntu on WSL (Windows Subsystem for Linux)?

A:
WSL does not support IME directly. However, GUI apps may accept Japanese input when combined with Windows’ IME and an X server (VcXsrv, X410, etc.).

That said, setup is complex, so WSL is generally best used with English input for CLI tasks.

Q5. Conversion candidates or predictive suggestions do not appear in Japanese input.

A:
Mozc prediction features may be disabled.

Fix:

1. Open Mozc settings:

ibus-setup

2. Enable “Suggestions” and “Auto-Learning” features
3. Save and restart IBus

7. Summary and Additional Resources

This article provided a detailed guide for resolving issues where Japanese input does not work on Ubuntu. Below is a summary of key points and helpful resources for further reference.

7.1 Summary of Key Points

To ensure Japanese input works correctly on Ubuntu, follow these steps:

1. Identify the cause

• Check if IME (Mozc, Fcitx) is installed
• Verify IME configuration
• Confirm keyboard layout settings
• Check for application-specific issues (Chrome, VS Code)

1. Configure Mozc properly

• Install ibus-mozc and add it to Input Sources
• Reload input method using ibus restart
• Switch Japanese input with Hankaku/Zenkaku or Ctrl + Space

1. Consider using alternative IMEs like Fcitx or Anthy

• Fcitx: lightweight and fast
• Anthy: useful in environments where Mozc cannot run

1. Perform troubleshooting when issues persist

• Restart IME with ibus restart or set engine via ibus engine mozc
• Disable Chrome hardware acceleration if input fails
• Reset IBus settings using dconf reset -f /desktop/ibus/

1. Check FAQ for additional solutions

• Sudden IME failures
• IME usage in WSL or Live USB environments
• Prediction settings not working

By following these steps, you can reliably restore Japanese input functionality on Ubuntu.

7.2 Additional Resources

If you need more information or want to check the latest Ubuntu documentation, refer to the following resources:

• Ubuntu Official Documentation
  https://help.ubuntu.com/
• Ubuntu Japanese Forum (Discussion and Q&A)
  https://forums.ubuntulinux.jp/
• Mozc Official Repository
  https://github.com/google/mozc
• Fcitx Official Documentation
  https://fcitx-im.org/wiki/Fcitx
• Linux Community Technical Blogs
• Qiita (Ubuntu tag): https://qiita.com/tags/ubuntu
• Ask Ubuntu (English Q&A): https://askubuntu.com/

7.3 Conclusion

For beginners, configuring Japanese input on Ubuntu can feel complicated. However, by following the procedures outlined in this guide step by step, most issues can be resolved.

If you still cannot solve the problem, consider seeking help on Ubuntu forums or Linux-related communities.

With proper configuration, you can enjoy a smooth Japanese typing experience on Ubuntu. Set up your environment and work comfortably!