What you’ll learn in this article
- Main Causes of Slow Internet During a Trip to Japan
- Points to Check First When You Can’t Connect
- Troubleshooting Methods You Can Try Immediately
- Points to Note for Free Wi-Fi, SIM, and eSIM
- Advance Measures to Prevent Problems
In Conclusion: Most Issues Are Due to “Temporary Environmental Factors” or “Setup Errors”
If your internet is slow or not working during your trip to Japan,
it’s often due to network congestion or incorrect settings.
It’s rare for the SIM or eSIM itself to be faulty.
If you stay calm and check, you can usually fix it yourself.
If you want to understand the overall picture of communication methods,
Recommended SIM Cards and How to Choose Them for Travelers to Japan [2026 Latest Edition]
please also refer to.
Main Causes of Slow Internet in Japan
Common causes include:
- Network congestion in tourist areas and around stations
- Weak signal underground or inside buildings
- Free Wi-Fi speed limits
- Data usage exhausted or speed limits reached
- Incorrect network or setting switches
The solutions vary depending on the cause.
Basic Checks to Make First
In the event of communication problems, check the following in order:
- Is Airplane Mode OFF?
- Is mobile data turned ON?
- Is the correct SIM / eSIM network selected?
- Have you used up your data allowance?
Often, this alone will solve the problem.
Solutions for Slow Internet in Tourist Areas and Congested Areas
In popular tourist destinations in Japan,
communication speeds may slow down depending on the time of day.
Solutions to try:
- Move to a slightly different location
- Reconnect at a different time
- Switch between Wi-Fi and mobile data
Especially in the evening and at night, congestion is likely, so
in many cases, it’s “just temporarily slow.”
If You Can’t Connect Underground or Indoors
The signal may be weak
in subways, underground malls, and large buildings.
Solution:
- Go above ground and reconnect
- Temporarily use the Wi-Fi in the station
- Wait a few minutes and try again
In most cases, it will recover if you change locations.
Points to Note When Using Free Wi-Fi
Free Wi-Fi tends to be
slow and unstable.
- Speeds drop dramatically when there are many users
- There are connection time limits
- Security concerns
Use free Wi-Fi as a supplement, and
it’s safer to have a SIM or eSIM for your main communication.
For more information,
see Is Free Wi-Fi in Japan Usable? A Summary of Points to Note for Travelers [2026 Edition].
Solutions When You Can’t Connect with SIM or eSIM
When using a SIM or eSIM, check the following:
- Network used (docomo / au / SoftBank)
- Does the plan require APN settings?
- Is the network switched to Japan?
In the case of eSIM,
Causes and Solutions for When eSIM Doesn’t Work in Japan | Explanation by iPhone and Android [2026 Edition]
also check.
Options if it still doesn’t improve
- Restart your device
- Contact support
- Consider another means of communication (SIM / Pocket WiFi)
If multiple people are using it,
Is Pocket WiFi Necessary for Traveling in Japan? Thorough Comparison with SIM and eSIM [2026 Edition]
refer to.
Advance Measures to Prevent Problems
It’s a good idea to check the following before you leave:
- Is it a compatible device?
- Network and area used
- Is there enough data?
- Have you checked the setup procedure?
You can check the data usage目安は、
How Much SIM Data Do You Need for Traveling in Japan? [2026 Edition]
.
Summary: Don’t Panic, Just Identify the Cause
- Most communication problems are temporary
- Setup errors and congestion are the main causes
- Basic checks often solve the problem
- Advance preparation is the best solution
To enjoy your trip to Japan with peace of mind,
make sure to double-check the communication methods that suit you in
Recommended SIM Cards and How to Choose Them for Travelers to Japan [2026 Latest Edition]
.
Recommended communication methods (frame to be filled in later)
*Replaced when affiliate program is introduced
- Company A: eSIM compatible with Japan (tentative)
- Company B: Nationwide SIM Card (Tentative)
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