Many people want to use LINE or WhatsApp to stay in touch with family and friends while traveling in Japan.
However, when considering a travel eSIM for Japan, you may feel anxious about questions like, "Can I use LINE with a data-only eSIM?" "Will my phone number change when I switch SIMs for WhatsApp?" "Can I make voice and video calls in Japan?"
In conclusion, as long as you have a Japan eSIM that can connect to the internet, you can generally use LINE and WhatsApp for messaging, voice calls, and video calls.
Many travel eSIMs for Japan are data-only, but since LINE and WhatsApp use internet connections, they can be used even without a Japanese phone number.
However, you need to be cautious about re-logging into the app, phone number verification, roaming settings for your usual SIM, and data usage.
This article will explain in detail how to use LINE and WhatsApp with a Japan eSIM during your trip and the points to be aware of during setup.
Can I use LINE and WhatsApp while traveling in Japan?
If you can use mobile data with a Japan eSIM, you can use LINE and WhatsApp as usual.
The main features available are as follows:
- Sending and receiving text messages
- Sending and receiving photos and videos
- Sharing location information
- Sending voice messages
- Voice calls
- Video calls
- Group chats
- Sending stickers and files
These features use internet communication rather than regular phone calls.
Therefore, even if your travel eSIM does not have a Japanese phone number, you can use it as long as you are logged into the app.
You can check the mechanism of Japan travel eSIMs in the Complete Guide to Japan eSIM.
Can I use a data-only eSIM?
Many Japan eSIMs for travelers are data-only products.
With a data-only eSIM, you cannot use voice calls or SMS that rely on regular phone lines.
However, since LINE and WhatsApp use the internet, you can use them if you meet the following conditions:
- The Japan eSIM is properly activated
- Your smartphone can connect to the internet
- You are logged into LINE or WhatsApp
- Mobile data for the app is allowed
| Feature | Data-only eSIM | eSIM with Phone Number |
|---|---|---|
| LINE Messages | Available | Available |
| LINE Voice & Video Calls | Available | Available |
| WhatsApp Messages | Available | Available |
| WhatsApp Voice & Video Calls | Available | Available |
| Regular Phone Calls | Generally Not Available | Depends on Product Conditions |
| SMS Sending/Receiving | Generally Not Available | Depends on Product Conditions |
If you want to make regular phone calls to stores or hotels in Japan, please check the eSIM with Phone Number.
Will my LINE account change if I switch to an eSIM?
Switching to a Japan eSIM for mobile data does not usually change your LINE account automatically.
If you are already logged into LINE on your device, you can continue to use messaging and calls using the internet connection of the Japan eSIM.
However, the following actions may require you to verify your identity or log in again:
- Deleting and reinstalling the LINE app
- Logging out of LINE
- Changing to a new smartphone
- Transferring your account
- Changing your phone number
During your trip, avoid deleting the app or logging out unless necessary.
Will my WhatsApp number change if I switch to an eSIM?
Switching to a Japan eSIM for mobile data does not automatically change the phone number registered with WhatsApp.
WhatsApp can use a different internet connection while maintaining the phone number verified during account registration.
Therefore, you can use your messages and calls with the Japan eSIM while keeping your usual phone number.
Even if a screen appears asking if you want to change your phone number when a new SIM is detected, if you do not need to change your number during your trip, please keep your current number.
Be cautious about phone number verification and SMS verification
If you are already using LINE or WhatsApp, switching to a Japan eSIM usually does not require re-verification.
However, if you reinstall, re-login, or change devices, you may need SMS or phone verification sent to your registered phone number.
With a data-only Japan eSIM, you cannot receive SMS sent to your registered number.
If you need to receive SMS on your usual SIM, you can keep the main line active using dual SIM functionality.
However, the costs for receiving SMS, voice calls, and maintaining the line while abroad vary by your usual carrier.
Settings for using Japan eSIM and your usual SIM together
If you have a dual SIM compatible smartphone, you may be able to activate both the Japan eSIM and your usual SIM simultaneously.
Here is a recommended configuration:
- Mobile Data: Japan eSIM
- Default Voice Line: Usual SIM
- SMS: Usual SIM
- Data Roaming for Japan eSIM: ON as needed
- Data Roaming for Usual SIM: OFF
- Automatic Switching of Mobile Data: OFF
With this configuration, you may be able to use LINE and WhatsApp with the Japan eSIM while receiving SMS and calls to your usual phone number.
However, if you answer or make calls with your usual SIM, you may incur international call charges.
Turn OFF data roaming for your usual SIM
When using a Japan eSIM, it is particularly important to be cautious about unintended international roaming with your usual SIM.
Even if you select the Japan eSIM for mobile data, if automatic line switching is enabled, there is a possibility that communication will occur through your usual SIM.
To prevent high international roaming charges, please check the following items:
- Select Japan eSIM for mobile data
- Turn OFF data roaming for your usual SIM
- Turn ON data roaming only for Japan eSIM
- Turn OFF automatic switching of mobile data
- Turn OFF Wi-Fi and check if you can communicate with Japan eSIM
For detailed setup instructions for Japan eSIM, please refer to the eSIM Setup Guide.
How much data do LINE and WhatsApp use?
If you are only sending text messages, the data usage for LINE and WhatsApp is relatively low.
On the other hand, using photos, videos, voice calls, and video calls will increase data consumption.
| Usage | Data Consumption | Notes |
|---|---|---|
| Text Messages | Very Low | Little impact on capacity for short trips |
| Stickers & Emojis | Low | Even if sent and received in large quantities, relatively low |
| Sending and Receiving Photos | Normal | High-quality photos are large in size |
| Sending and Receiving Videos | High | Be cautious with long or high-quality videos |
| Voice Calls | Normal | Increases with long calls |
| Video Calls | High | Varies with video quality and usage time |
If you mainly use LINE and WhatsApp messages, Google Maps, and translation apps, a small to medium capacity eSIM should be sufficient.
If you make video calls daily or frequently send and receive videos, consider a large capacity or unlimited plan.
For data usage by app, please refer to the Estimated Data Usage.
Estimated data capacity needed based on travel days
| Travel Days | Message Focus | Using Photos & Voice Calls | Frequent Video Calls |
|---|---|---|---|
| 3 Days | About 1GB | 1-3GB | Over 3GB |
| 5 Days | 1-3GB | 3-5GB | Over 5GB |
| 7 Days | About 3GB | 3-5GB | 5-10GB or more |
| 14 Days | 3-5GB | 5-10GB | Over 10GB or unlimited |
| 30 Days | 5-10GB | 10-20GB | Large capacity or unlimited |
In reality, you will also use Google Maps, social media, web searches, translation apps, and more in addition to LINE and WhatsApp.
Consider your overall usage during your trip and choose a comfortable capacity.
You can check plans by days and capacity at Japan eSIM Pricing and Plan Comparison.
Points to note when using voice and video calls
Quality varies depending on the communication environment
The quality of voice and video calls can change based on signal strength and network congestion.
In basements, mountainous areas, crowded stations, or deep inside buildings, you may experience temporary audio dropouts or frozen video.
Video calls consume a lot of data
Video calls use more data than text messages or voice calls because they transmit both video and audio simultaneously.
For long video calls, it is advisable to use a reliable Wi-Fi environment, such as in hotels or airports, to reduce data consumption on your eSIM.
Be cautious of background communication
LINE and WhatsApp communicate in the background to receive new messages and calls.
Usually, this does not consume a large amount of data, but if automatic downloads of photos and videos are enabled, data consumption may increase.
How to save on data usage
Turn OFF automatic downloads for photos and videos
If you receive many photos and videos in group chats, automatic downloads can consume data capacity.
Limit automatic downloads during mobile data usage in the app settings.
Send and receive videos while connected to Wi-Fi
It is recommended to send and receive long or high-quality videos while connected to Wi-Fi, such as in hotels.
Shorten video call duration
During mobile communication, focus on voice calls and use video calls only for the necessary duration to reduce data usage.
Check cloud backup settings
If chat history or photo backups are executed over mobile data, it may increase data usage.
It is recommended to set backups to run only when connected to Wi-Fi.
Use low data mode
Using your smartphone's low data mode or data saver feature can help reduce background communication for apps.
If you don't receive notifications from LINE or WhatsApp
If you do not receive notifications after switching to a Japan eSIM, please check the following items:
- Can you connect to the internet with the Japan eSIM?
- Are app notifications allowed?
- Is mobile data for the app allowed?
- Is background communication restricted?
- Is the app stopped due to power-saving mode?
- Is focus mode or do not disturb mode enabled?
- Is the app updated to the latest version?
If communication is possible but notifications are not coming through, check the notification settings for the app and smartphone.
If LINE or WhatsApp won't connect
If you cannot open not only the app but also websites or Google Maps, there may be an issue with the connection settings for the Japan eSIM.
- Turn ON the Japan eSIM line
- Select Japan eSIM for mobile data
- Turn ON data roaming for Japan eSIM
- Toggle airplane mode ON and OFF
- Restart your smartphone
- Check the APN if necessary
- Restart the app
Even if you cannot connect, do not delete the eSIM immediately based on your own judgment.
The QR code for the travel eSIM may only be usable once. If you delete it, you may not be able to reinstall it with the same QR code.
For detailed troubleshooting, please refer to Troubleshooting Japan eSIM Connection Issues.
Things to check before your trip
Before departing for Japan, make sure that LINE and WhatsApp are functioning properly.
- Can you log into the app?
- Do you know your registered phone number?
- Have you checked your password and authentication information?
- Have you backed up your chat history?
- Is the app updated to the latest version?
- Can you receive SMS on your usual SIM?
- Have you checked the setup method for the Japan eSIM?
To prevent troubles during your trip, it is recommended not to delete the app or change your phone number just before departure.
How much capacity should I choose for Japan eSIM?
If you mainly use text messages on LINE and WhatsApp, data usage can be kept relatively low.
However, during your trip to Japan, you will also use maps, transit guides, translations, and social media, so it is important to choose according to the number of travel days.
- 3 Days: 1-3GB
- 5 Days: 3-5GB
- 7 Days: 3-5GB
- 10-14 Days: 5-10GB
- 30 Days: 10-20GB or more
If you make video calls daily or frequently send and receive videos, choose a larger capacity than this.
You can check the currently available plans at Japan eSIM Products and Pricing Plans.
When is a phone number eSIM necessary?
If you only use LINE and WhatsApp, a data-only eSIM is generally sufficient.
On the other hand, a plan with a phone number is convenient in the following cases:
- If you want to make regular phone calls to stores or hotels in Japan
- If you want to receive calls from delivery services
- If you want to perform SMS verification with a Japanese phone number
- If you need a Japanese phone number for work
- If you frequently use regular calls during a long stay
However, even with a product that has a phone number, SMS verification may not be available for all services. Please check the usage conditions before purchasing.
Check if your device supports eSIM
To use a Japan eSIM, your smartphone must support eSIM and be unlocked.
Even with the same model name, the eSIM compatibility may vary depending on the country of sale and model.
Before purchasing, please check the List of eSIM-Compatible Devices.
Frequently Asked Questions about LINE, WhatsApp, and Japan eSIM
Can I make LINE calls with a data-only eSIM?
Yes. If you can connect to the internet with a Japan eSIM, you can use LINE voice and video calls.
Can I make WhatsApp calls with a data-only eSIM?
Yes. You can use messaging, voice calls, and video calls.
Will my LINE friends disappear if I switch to a Japan eSIM?
Changing the mobile data connection does not usually cause friends or chats to disappear.
However, if you delete the app or change devices, please check your backup and transfer settings in advance.
Do I need to change the number registered with WhatsApp?
If you are only using the travel Japan eSIM for data communication, you generally do not need to change your registered number.
Can I use LINE and WhatsApp if I remove my usual SIM?
If you are already logged in and can use data communication with the Japan eSIM, you may be able to use them.
However, if re-verification is required, you may not be able to receive SMS sent to your registered number.
Do I need a Japanese phone number to use LINE and WhatsApp?
If you already have an account, a Japanese phone number is generally not required.
Is 1GB enough for just messaging?
If you mainly use text messages on LINE and WhatsApp, 1GB may last for a long time.
However, if you also use maps, social media, photos, and videos during your trip, choose a comfortable capacity that matches the number of travel days.
What should I do if calls are dropping?
Move to an area with better signal and restart the app. Switching from video calls to voice calls may stabilize the connection.
Is it okay to delete the Japan eSIM?
Do not delete it before you finish using it or during connection troubles. You may not be able to reuse the same QR code.
For other questions, please refer to Frequently Asked Questions about eSIM.
Summary | You can use LINE and WhatsApp with a data-only eSIM
Even while traveling in Japan, as long as you can connect to the internet with a Japan eSIM, you can use LINE and WhatsApp.
With a data-only eSIM, you can use the following features:
- Text messaging
- Sending and receiving photos and videos
- Voice calls
- Video calls
- Sharing location information
You do not need to change the phone number registered with LINE or WhatsApp immediately after switching to an eSIM.
However, during re-login or app reinstallation, you may need SMS verification sent to your registered number.
Also, to prevent high international roaming charges, please turn OFF data roaming and automatic switching of mobile data for your usual SIM.
For information on setting up and using Japan eSIM, please check the Complete Guide to Japan eSIM.
You can choose a data plan that fits your travel days from Japan eSIM Products and Pricing Plans.
