How to Set Up Japanese Input with Mozc on Ubuntu | Installation, Switching, and Troubleshooting

By 佐川 直弘 | Naohiro Sagawa (運営者)

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1. Introduction | What This Article Will Help You Solve

If you’re new to Ubuntu or transitioning from Windows, you might be struggling with setting up Japanese input or enabling Mozc properly.

In this article, we will explain in detail how to set up Japanese input on Ubuntu in a beginner-friendly way. Additionally, we will cover the differences between Mozc and Fcitx 5 as well as troubleshooting tips. By the end of this guide, you’ll have a smooth Japanese input environment on Ubuntu.

2. How to Set Up Japanese Input on Ubuntu [2025 Edition]

To type in Japanese on Ubuntu, you need to install an appropriate Input Method Editor (IME). The recommended standard IME for Ubuntu is Mozc.

2.1 What is Mozc?

Mozc is the open-source version of Google Japanese Input and is widely used as the standard Japanese input system on Ubuntu. It is lightweight and offers relatively high conversion accuracy, making it a great choice for beginners.

2.2 Installing Mozc

In most cases, Mozc is not pre-installed on Ubuntu. Follow these steps to install it:

2.2.1 Install Mozc via Terminal

First, open a terminal and enter the following commands:

sudo apt update
sudo apt install ibus-mozc

These commands will fetch the latest package information and install Mozc.

2.2.2 Restart Your System

After installing Mozc, restart your system to apply the changes properly.

sudo reboot

2.3 Applying the IME Settings

After restarting your system, follow these steps to configure Mozc:

1. Open the Settings App
   Go to the “Settings” app and navigate to the “Region & Language” section.
2. Add an Input Source
   Click the “+” button under “Manage Input Sources” and select “Japanese (Mozc).”
3. Set Mozc as the Default
   Move Mozc to the top of the list to make it the default input source.

Now, your Japanese input environment is ready!

3. Configuring Mozc on Ubuntu

3.1 Setting Up Mozc Using GUI

If you’re not comfortable using the terminal, you can configure Mozc using the Graphical User Interface (GUI).

1. Open the “Settings” App

• Click on the “Application Menu” at the bottom left corner and open “Settings.”
• Select “Region & Language.”

1. Add an Input Source

• Click the “+” button.
• Search for “Japanese (Mozc)” and add it.

1. Change Input Source Priority

• Move “Mozc” to the top of the list.

This method allows you to set up Mozc without using the terminal.

4. Differences Between Mozc and Fcitx 5 | Which One Should You Use?

In addition to Mozc, Ubuntu also supports another IME called Fcitx 5. Below is a comparison of Mozc and Fcitx 5 to help you choose the right one.

4.1 Features of Mozc

• The default IME for Ubuntu, offering stable performance.
• Moderate conversion accuracy, but lacks a customizable dictionary.
• Simple settings, making it ideal for beginners.

4.2 Features of Fcitx 5

• Lightweight and fast performance.
• More customization options compared to Mozc.
• Widely used in Linux environments, though it may have compatibility issues with some applications.

In conclusion, Mozc is recommended for beginners, while those who prefer more customization may find Fcitx 5 a better fit.

5. Troubleshooting When Japanese Input Doesn’t Work on Ubuntu

5.1 If Mozc Is Not Responding

1. Check the system settings to ensure the input source is correctly configured.
2. Restart Mozc by running the following command in the terminal:

ibus restart

5.2 If the Candidate Window Does Not Appear

Open Mozc’s settings and ensure the “Input Mode” is set to “Hiragana.”

5.3 If You Cannot Type in Certain Applications (e.g., Firefox, LibreOffice)

1. Close and restart the affected application.
2. If the issue persists, consider trying Fcitx 5 instead.

5.4 If Mozc Stops Working After Installing Fcitx 5

Fcitx 5 may conflict with Mozc. Try removing unnecessary IMEs with the following commands:

sudo apt remove fcitx
ibus restart

6. Frequently Asked Questions (FAQ)

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

A: Run the ibus restart command. If that doesn’t work, restart your PC.

Q2: Are there alternatives to Mozc?

A: Yes, you can use Fcitx 5 or Anthy as alternative Japanese input methods.

Q3: Do different Ubuntu versions affect Japanese input?

A: Yes. In newer versions (Ubuntu 24.04 and later), Fcitx 5 is becoming the default IME.

Q4: How can I make Ubuntu’s Japanese input similar to Windows?

A: You can tweak Mozc’s settings to make it function similarly to Windows IMEs.