What is an eSIM? Step-by-Step Guide to Installing an eSIM on iPhone and Android

Ordered a SIM today and flying tomorrow? With physical SIMs, you're out of luck — the post office won't deliver in time. But with an eSIM, it takes just a few minutes from placing your order to getting a cellular signal in Japan. This article breaks down everything about eSIMs in the simplest way possible and guides you step-by-step through setup — even if you've never heard the word "eSIM" before.

1. What is an eSIM, simply put?

A traditional SIM is a small plastic card you insert into your phone slot. An eSIM is a "digital SIM" built directly into your phone — instead of inserting plastic, you scan a QR code to "load" carrier information onto that built-in chip. The end result is identical: signal and data access. The key differences:

• Instant email delivery: no waiting for shipping, no risk of losing it.
• No SIM ejector tool needed, and no worry about dropping a tiny plastic SIM.
• Store multiple eSIMs on one device: keep your Vietnamese SIM in the physical slot to receive OTPs, while using your Japan eSIM as your primary network — running side by side on the same phone.
• Quickly switch plans or carriers: it's just a few taps on your screen.

2. Is your phone eSIM compatible?

Here is a list of popular eSIM-compatible devices (not exhaustive, but covers most):

• iPhone: iPhone XR, XS (2018) and newer — including iPhone SE 2020/2022, iPhone 11, 12, 13, 14, 15, 16, 17.
• Samsung: Galaxy S20 and newer, Note 20, Z Fold/Flip series, A54/A55, and many newer A-series models.
• Google Pixel: Pixel 3 and newer.
• Other brands: many Oppo, Xiaomi, and Sony models from 2021 onwards support eSIM — double-check your specific model.

The surest way to check in 30 seconds

• iPhone: Go to Settings → Cellular (or Mobile Data) — if you see "Add eSIM", your phone is compatible.
• Android: Go to Settings → Connections/Network → SIM Manager — if you see "Add eSIM", you're good to go. Or dial *#06#: if an EID (a 32-digit number) appears on screen, your phone supports eSIM.

Important note for phones purchased in Vietnam: Some imported/hand-carried models from mainland China do not support eSIM even if they share the same model name. Additionally, your phone must be unlocked — phones bought on contract or installment plans may be network-locked. Check under Settings → General → About → Carrier Lock (iPhone), which should say "No SIM restrictions".

3. Before installation: Prepare 3 things

1. The email containing your eSIM QR code sent by the provider after ordering. Do not delete this email — you may need it if you switch phones.
2. WiFi connection: Since cellular network isn't active during setup, you'll need WiFi (home, hotel, or hotspot from another phone).
3. A second screen to display the QR code: Open the email on a computer or a friend's phone to scan it. If you only have one device, use the manual input method in Section 6.

4. How to install an eSIM on iPhone — 6 Steps

1. Connect to WiFi, go to Settings → Cellular → Add eSIM.
2. Select Use QR Code to open the camera.
3. Scan the QR code in your email. When "Activate eSIM" appears, tap Continue.
4. Wait 1–2 minutes for automatic activation. Set a label for easy identification, e.g., "Japan SIM".
5. Set your Japan eSIM as the default line for Cellular Data; keep your Vietnamese SIM (if any) for calls/SMS only.
6. Turn on Data Roaming for the Japan eSIM if instructed — for some travel eSIMs, this step is mandatory to get service.

Once complete, the status bar showing signal bars with 4G/5G indicates success. If you have signal bars but no internet access, check Section 7.

5. How to install an eSIM on Android (Samsung example) — 6 Steps

1. Connect to WiFi, go to Settings → Connections → SIM Manager.
2. Tap Add eSIM → Scan QR code.
3. Scan the QR code in your email, then tap Add to confirm.
4. Wait 1–2 minutes for the profile to download, then turn on the newly added eSIM.
5. In SIM Manager, set your Japan eSIM for Mobile Data.
6. Check and turn on Data Roaming if required by the instructions.

On Pixel and other Android devices, the steps are similar: Settings → Network & internet → SIMs → Add eSIM.

6. Can't scan the QR code? Enter manually in 2 minutes

A QR code actually contains two text strings: the SM-DP+ Address and an Activation Code. Reputable providers always include these details below the QR code in the email. How to enter manually:

• iPhone: Settings → Cellular → Add eSIM → Use QR Code → Enter Details Manually (small text at the bottom).
• Android: On the QR scanner screen, select Enter code manually / Enter details manually.

Copy and paste both strings into their respective fields — the result is identical to scanning the QR code.

7. Installed but no internet? Check in this order

1. Did you set the eSIM for Mobile Data? The #1 beginner mistake: the eSIM is installed, but the phone still routes data through the old SIM.
2. Is Data Roaming turned on for the eSIM? Many travel eSIMs require roaming enabled to get internet access.
3. Do you need to set up APN? Some carriers require APN settings (Access Point Name). Check your instruction email: go to Settings → Cellular → Cellular Data Network, and enter the APN, username, and password as provided.
4. Restart your phone: Sounds basic, but it solves over half of all issues.
5. Try toggling Airplane Mode on/off to force the phone to reconnect to the network.
6. Still not working? Take a screenshot of your settings and message support — at HD TELECOM, our Vietnamese team is on standby on Zalo/LINE to guide you specifically for your phone model.

8. Three frequently asked questions about eSIM

Will I lose my eSIM if I upgrade to a new phone?

eSIMs are tied to the device, so changing phones requires transferring the eSIM to your new device. Newer iPhones offer a quick transfer feature between iPhones; in other cases, you usually need a new QR code issued — contact your provider, typically free or for a small fee.

What if I accidentally delete my eSIM?

Don't panic — your plan data lives on the carrier's side, not inside your phone. Contact your provider to re-issue an activation code and you'll be back online.

How many eSIMs can one phone use simultaneously?

Most phones can store multiple eSIM profiles, but only 1–2 can be active at the same time. For example, iPhone 13 and newer support dual active eSIMs, or 1 eSIM + 1 physical SIM. Perfect for "Vietnamese SIM for OTPs + Japan eSIM for internet".

Conclusion

eSIM is the fastest way to get connected in Japan: order online today, scan the code, and start using it immediately without waiting for delivery. If your device is compatible, don't hesitate to choose an eSIM over a physical SIM. And if you still feel uncertain about any step, just message HD TELECOM with your phone model — we'll send you visual guides customized for your device, entirely in Vietnamese.