Updated: 2025-03-10 12:26:46
If you are traveling to Japan, you will need to rent a pocket Wi-Fi device or buy a SIM card or eSIM to ensure stable communication while in Japan. Renting a pocket WiFi device allows you to connect multiple devices to the internet, which is very convenient when traveling with family or friends in Japan. However, eSIMs have become quite popular recently.
During your stay in Japan, you'll likely want to stay in touch with your family or friends from back home. WhatsApp is a commonly used communication app in such cases. Some people are concerned about whether they can use WhatsApp with an eSIM while in Japan. In this article, we will summarize information about eSIMs in Japan and WhatsApp.
Since WhatsApp does not require a phone number, you can make free voice and video calls while in Japan. However, WhatsApp must already be installed on your smartphone, and the phone number must be authenticated. Be sure to complete WhatsApp's authentication before coming to Japan. As long as you have an internet connection, you can use WhatsApp. Even if you remove your SIM card or switch to an eSIM for use in Japan, you can continue using your WhatsApp account created with the number you used for authentication.
WhatsApp app installation: Both users must have WhatsApp installed.
Internet connection: You need either Wi-Fi or mobile data. Using Wi-Fi will save on data costs.
Contact registration: You need to register the other person's phone number in international format (with the country code).
WhatsApp calls are free: No charges for using WhatsApp, whether domestic or international.
WhatsApp calls use VoIP (Voice over Internet Protocol), which means they are made using data transmission over the internet.
With WhatsApp, you can receive calls from anywhere in the world. Even if you're in Japan, you can receive calls from family or friends abroad. The recipient must be connected to the internet, and the caller must also be using WhatsApp.
WhatsApp calls use VoIP (Voice over Internet Protocol), so they cannot connect to regular phone lines.
Long voice or video calls consume a lot of data, so it's essential to use WhatsApp over a Wi-Fi connection.
If you need to make long calls, it's advisable to buy an eSIM with a large data plan or rent a Pocket Wi-Fi.
IIf you're using an eSIM for communication in Japan, here's a summary of the data usage you can expect:
| Feature | Data Usage | Notes |
|---|---|---|
| Text Messages | Approx. 1KB / message (without media) | Minimal data consumption, negligible impact even with hundreds of messages sent |
| Voice Calls | 0.15MB - 0.5MB / min (150KB - 500KB) | Uses less data than video calls, stable communication |
| Video Calls | 3MB - 6MB / min | Consumes the most data; increases further with high-resolution settings |
| Media Sharing |
Images: 50KB - 500KB / image Videos: 500KB - 2MB / min (depending on resolution) Audio Files: 100KB - 1MB / min |
Data usage varies based on file size and resolution, videos consume the most data |
| Background Data | Approx. 1KB / 24 hours | Minimal data usage while running in the background |
The most data is consumed by video calls. Here's the data usage needed for a 1-hour video call.
| Feature | Data Usage (Per Hour) |
|---|---|
| Video Calls | 180MB - 360MB |
IIf you plan to have daily 1-hour video calls on WhatsApp during your stay in Japan, you should purchase an eSIM or SIM card with at least 1GB of data per day, or rent a Pocket Wi-Fi.
