A travel eSIM is a second line you add to your phone for internet abroad. Your own number stays on your existing SIM for calls and two-factor codes. Install it on wifi before you fly, switch it on when you land, and check three things before buying, which host network the plan uses, whether tethering is allowed, and whether your phone is carrier-unlocked.
An eSIM is a SIM profile downloaded into the phone instead of pushed into a tray. A travel eSIM is a data-only one bought for a trip. It sits alongside your existing line, which keeps carrying your number, your calls and the SMS codes your bank sends. Nothing about the home line has to change, and the mistakes travellers make almost all come from changing it anyway.
Our estimate, not a measurement. Maps, messaging, transit apps and a normal amount of browsing come to roughly half a gigabyte a day. Streaming video or uploading photo albums over mobile is what turns that into two or three. A ten-day trip on ordinary use lands near five gigabytes, and an unlimited plan only pays for itself if you know you are the second kind of traveller. The country guides below give observed prices for the plan sizes that follow from this.
Installing means downloading the profile onto the phone, and it needs a working internet connection, which is why you do it at home on wifi and not at the arrival gate. Activating means switching that line on and letting it register on a network at your destination, and on most plans that second step is what starts the validity clock. Days at home cost nothing. Days after activation cost money.
Read on the providers’ own plan pages on 15 September 2026. Both rows below are reference providers we earn nothing from, and both put the trigger in writing, which is more than most plan pages do.
| Plan | Price | One day costs | What starts the clock |
|---|---|---|---|
| Ubigi Japan, unlimited, 15 days | US$39 | US$2.60 | First attach. The page says the plan “will automatically activate upon arrival in a destination covered by the plan, with the validity period starting from that moment”, and that an unactivated plan expires six months after purchase. |
| Nomad Japan, unlimited, 14 days | US$41 | US$2.93 | First attach, with a deadline. The page says the plan “will start automatically once connected to the destination network”, and that you must activate within 60 days of purchase, after which it activates itself and the expiry begins. |
That is the arithmetic of the mistake. Switch the Ubigi line on the night before a long-haul flight and you have spent US$2.60 of a US$39 plan sitting at home, one fifteenth of what you paid, for nothing. On the fourteen-day Nomad plan the same evening costs US$2.93. Neither will ruin a trip, and neither is the real reason to wait.
The real reason is that not every plan works the way these two do. Find the sentence on the plan page before you pay, because there are only three things it can say, and they are not equivalent.
Two edge cases follow from the third wording rather than from ours. A regional or global plan treats arrival in any covered destination as arrival, so a layover inside the coverage area can start the clock before you reach the country you bought it for. And a plan left installed but never switched on does not sit there forever, and both deadlines run from the purchase date rather than from the install, six months for Ubigi and 60 days for Nomad, both stated on the pages above.
So the sequence is install at home on wifi, leave the travel line switched off through the airport and the flight, and turn it on with data roaming enabled once you are on the ground. Installing alone does not attach to anything. Our per-day figures come from the plan prices as displayed, with no coupon and no first-order discount, which is the same rule as the rest of the site, set out in our method.
Sources, Ubigi Japan unlimited 15 days and Nomad Japan eSIM, both read 15 September 2026.
No. A data-only travel eSIM adds a second line for internet. Your existing number stays on your physical SIM or on your primary eSIM, and it remains the number people reach you on, provided you leave that line enabled.
Not by itself. A data-only travel eSIM carries no phone number, so it receives nothing at all, no texts and no codes. Bank codes still go to your home number, and they arrive only while that line stays enabled and your carrier allows inbound roaming for texts. Disabling the home line is what breaks them. On iPhone keep Turn On This Line switched on for the home line. On Android set SMS preference to the home SIM.
No, and you should not. Dual SIM is the point, the physical SIM keeps your number and your codes, the eSIM carries the data. Removing the physical SIM is the single most common way travellers lock themselves out of their own accounts.
Dial *#06# and look for an EID. If there is one, the hardware supports eSIM. The other requirement is that the phone is carrier-unlocked, which is separate and which the EID does not tell you. Check both before you buy a plan.
Install before you fly, activate on arrival. Installation needs a working internet connection, which is exactly what you may not have at the arrival airport. Most providers let you install the profile early and start the validity period later.
Some plans allow it, some block it, and a few permit it only up to a cap. If you plan to share the connection with a laptop or a travelling companion, check the tethering line in the plan terms before buying, because it is rarely mentioned in the headline.
Almost always a daily allowance at full speed, then a throttle. The providers in our tables state anything from 3 GB a day at full speed then 1 Mbps, to a fair-use policy with no threshold published at all. A plan that does not state the threshold has not told you what you are buying.
This is the question that decides coverage outside the cities, and the plan page often does not answer it. Each of our country guides records which network each provider names, and which providers name none.