How to Set Up Japanese Input on Ubuntu (Mozc & IBus Complete Guide)

1. Checking and Installing the Japanese Input Environment

To use Ubuntu comfortably in Japanese, it is essential to properly configure the Japanese input environment. In this section, we explain how to check the current input method and how to install the Japanese input method “Mozc.”

How to Check the Current Input Method

First, check which input method is currently used in your Ubuntu environment. Ubuntu generally uses a framework called “IBus (Intelligent Input Bus).”

Follow these steps to check:

1. Open “Settings” from the “Applications Menu” in the lower-left corner.
2. Select “Region & Language.”
3. Check the “Input Sources” section to see whether “Japanese (Mozc)” or “Japanese (Anthy)” has already been added.

If Japanese input is not listed here, you need to install Mozc in the next step.

How to Install the Japanese Input Method “Mozc”

Mozc is an open-source Japanese input conversion engine based on Google Japanese Input and is widely used as the standard Japanese input environment on Ubuntu.

You can install it by following the steps below:

1. Open the terminal.
2. Enter the following commands in order:

sudo apt update
sudo apt install ibus-mozc

apt update updates the package information, and apt install installs the ibus-mozc package.

3. After installation is complete, log out or restart the system to apply the changes.

Confirming Input Method Activation

After logging in again, open the “Region & Language” settings once more and check whether “Japanese (Mozc)” has been added to the input sources. If it appears, the installation was successful.

If “Japanese (Mozc)” is not listed, click the “+” button to add it manually.

2. Adding Japanese (Mozc) to Input Sources

After installing Mozc, you must add “Japanese (Mozc)” to Ubuntu’s input sources to actually use Japanese input. Without this step, Japanese input will not be available even if Mozc is installed.

This section explains how to add it clearly and step by step.

Steps to Add an Input Source from “Region & Language”

1. Open “Settings” from the “Applications Menu” in the lower-left corner.
2. Click “Region & Language” in the sidebar.
3. Click the “+” button under the “Input Sources” section.

A list of available languages and input methods will appear.

4. Search by typing “Japanese” or select “Japanese” from the category list.
5. Select “Japanese (Mozc)” from the list and click “Add.”

This adds “Japanese (Mozc)” to your input sources, allowing you to type Japanese by switching the keyboard input.

Pay Attention to Input Source Order

Input sources are prioritized in the order they are added. For example, if “Japanese (Mozc)” is at the top, Japanese input may be enabled by default at startup. Depending on your use case, this may be convenient or inconvenient, so adjust the order as needed.

You can change the order by dragging and dropping the input sources in the list.

Check the Input Indicator

In the top-right panel (top bar), an indicator showing the current input source (for example, “EN” or “あ”) is displayed. Clicking it allows you to easily switch between available input sources.

If “Japanese (Mozc)” appears here, the setup is complete.

3. How to Switch to Japanese Input

Once Mozc is installed and added as an input source, you can switch between Japanese and English input. This section explains the default switching methods and how to customize shortcut keys.

Default Switching Methods

Ubuntu provides predefined shortcut keys to easily switch input sources. To enable Japanese input, try the following:

• “Super (Windows key) + Space”
• The “Half-width / Full-width” key (on Japanese keyboard layouts)

Normally, pressing these keys switches the input indicator from “EN (English)” to “あ (Japanese).” After switching, you can start typing Japanese.

Note: On Japanese keyboard layouts, the “Half-width / Full-width” key is available. On English layouts, “Super + Space” is generally used. Choose the method that matches your keyboard.

Checking and Changing Current Shortcuts

If you want to check which shortcut keys are currently assigned, follow these steps:

1. Open “Settings” → “Keyboard.”
2. Look for “Switch input source.”
3. Here, you can see the currently assigned shortcut.

If the shortcut conflicts with another function or you want to customize it, you can reassign the key on the same screen.

Customization via Mozc Settings

Mozc itself also provides key configuration options. To open the Mozc settings:

1. Click the input indicator in the top-right corner (for example, “あ” or “EN”).
2. Select “Mozc Settings” from the menu.

In the Mozc settings, select the “Keymap” tab to customize keys for input mode switching and candidate window operations. For example:

• Alphanumeric ⇔ Japanese input: Ctrl + Space
• Hiragana ⇔ Katakana: F7 / F8

These customizations allow you to create a more comfortable input environment.

Visually Confirming Input Mode Status

The most reliable way to check whether you are in English or Japanese input mode is to look at the input indicator in the top-right corner.

• “EN” → English input
• “あ” or “A” → Japanese input (Mozc)

If the indicator does not switch, recheck your shortcut settings and input source priority.

4. Troubleshooting

Even after setting up Japanese input on Ubuntu, you may encounter issues such as being unable to switch input modes or type Japanese. This section explains common problems and their solutions.

What to Check If Japanese Input Does Not Work

1. Mozc Is Not Installed Correctly

First, confirm whether ibus-mozc is installed by running the following command:

dpkg -l | grep ibus-mozc

If no output appears, reinstall it using:

sudo apt update
sudo apt install ibus-mozc

After installation, be sure to log out or restart. Mozc may not activate until you log in again.

2. “Japanese (Mozc)” Is Not Added to Input Sources

Check “Settings” → “Region & Language” and confirm that “Japanese (Mozc)” is listed under input sources. If not, add it again using the “+” button.

Keyboard Shortcuts Do Not Respond

1. Shortcut Conflicts with Other Applications

If the key assigned to “Switch input source” conflicts with another shortcut, input switching may not work correctly.

Go to “Settings” → “Keyboard” → “Switch input source” and change it to a non-conflicting key combination (for example, Ctrl + Space).

2. Input Mode Is Hard to Identify Visually

On English keyboard layouts, the lack of a “Half-width / Full-width” key can make switching less intuitive. Make it a habit to check the input indicator (“EN” or “あ”) in the top-right corner to avoid confusion.

No Conversion Candidates Appear While Typing

This may indicate that the Mozc process is not running correctly. Restart the related processes with the following command:

ibus restart

After that, try typing Japanese again in a terminal or text editor and check whether conversion candidates appear.

Last Resort: Reset Settings

If the issue still cannot be resolved, you can reset the IBus and Mozc settings and reconfigure them.

rm -r ~/.config/ibus
ibus restart

Note that this command resets your personal IBus settings, so be careful if you have other custom configurations.

5. Frequently Asked Questions (FAQ)

Configuring Japanese input on Ubuntu can be confusing for first-time users. Here are answers to some of the most common questions.

Q1. How do I enable Japanese input on Ubuntu?

A.
First, install ibus-mozc by running the following commands:

sudo apt update
sudo apt install ibus-mozc

Then, add “Japanese (Mozc)” from “Settings” → “Region & Language.” After logging out or restarting, Japanese input will be available.

Q2. How can I switch Japanese input using keyboard shortcuts?

A.
By default, you can switch using “Super (Windows key) + Space” or the “Half-width / Full-width” key. If these do not work, you can customize the shortcut in “Settings” → “Keyboard.”

You can also assign a custom key such as “Ctrl + Space” in the Mozc settings.

Q3. Japanese input suddenly stopped working. What should I do?

A.
Check the following in order:

1. Whether Mozc is installed
2. Whether “Japanese (Mozc)” is added as an input source
3. Try restarting Mozc with ibus restart
4. Check for shortcut key conflicts

If the issue persists, resetting the IBus settings may help (note that this resets your configuration).

Q4. Can I use Japanese input systems other than Mozc?

A.
Yes. Ubuntu also supports “Anthy” and “fcitx-mozc.” However, Mozc is highly regarded for its conversion accuracy and overall usability, making it the recommended choice, especially for beginners.

Q5. Conversion candidates do not appear while typing. Why?

A.
The Mozc process may not be functioning correctly. Try restarting it with:

ibus restart

Also, some applications may not display conversion candidates properly. Testing in a different text editor can help identify the cause.