Before a trip, the hard part is rarely “can I scan a QR code?” It’s these three questions:
When should I install? When is the plan actually activated? When do the validity days start?
Some travelers assume the clock starts the moment they scan. Others assume nothing starts until they land. Both can be wrong. What matters is the plan’s activation / validity rule—and different carrier options for the same country can differ.
This guide separates install vs activate using the wording on Jeko product pages, and maps the three most common ways validity starts so you do not burn days early.
(Basics: What is an eSIM. Setup: iPhone / full activation guide.)
Install ≠ activate
| Step | What you do | Where |
|---|---|---|
| Install | Scan the QR / enter the activation code to add the eSIM profile | Stable Wi‑Fi (home or airport) is safer |
| Activate / start using | Turn the eSIM on, switch mobile data to it, enable data roaming if needed, and connect locally | After arrival, inside coverage |
Most Jeko FAQs say something like:
Install by scanning the QR on stable Wi‑Fi; after arrival, turn that eSIM on and switch mobile data to it.
The default overview notice is:
We recommend installing and setting up the eSIM before departure, then activating it after arrival.
Default playbook: install early, turn the line on after landing—unless your option is “validity starts on download/install,” in which case install only when you are ready.
How validity days are counted (three common patterns)
Always read the product page validity policy and activation notes. On Jeko you will mostly see:
1. Starts after connecting and generating data (most common)
Typical product wording:
Validity starts once the eSIM connects to a supported network and begins generating data traffic.
Examples:
- Korea total and Korea daily: FAQ notes validity starts after connecting; install early is fine if you leave the line off until arrival.
- Vietnam Vinaphone unlimited and Vietnam daily (local): start after connect + data (unless a specific option adds a redeem/scan deadline).
- Japan unlimited (AU / longer plans): often connect-and-data; some SoftBank / APN plans also say activate when you connect after arrival.
- Turkey and South Africa: you may install early, but turn mobile data off so validity does not start early.
Practical tip: scan in Taiwan → immediately turn that eSIM’s mobile data / line off → turn it on after landing.
2. Starts immediately after download / add (easy to start too early)
Do not assume “I have not landed, so it is fine.” These pages say validity begins on download or as soon as the eSIM is added.
- Thailand unlimited — Truemove H local number: validity/billing starts from install; do not install outside coverage or the plan may become unusable.
- Vietnam Viettel: “validity starts immediately after download—install only when ready.”
- Vietnam Mobifone local number (see Vietnam total): starts on download; after arrival you often dial 900 then 1; there may also be a “activate within 30 days of redeem” window.
Practical tip: install only when you are ready to use data, and inside coverage for number/tourist plans that require it.
3. A redeem / scan-within-X-days window
Some plans add a deadline to scan or activate after redeem, on top of connect-based or download-based rules. Vietnam local FAQs call this out explicitly. Read the order email and product page as soon as you buy.
Taiwan first or after landing?
| What the product page says | What to do |
|---|---|
| Starts on connect/data; early install OK if data is off | Install early, keep data off, activate after landing (Jeko default) |
| Install/activate after arrival | Prefer landing; if already installed, confirm that line’s data is off |
| Starts on download/add; do not install outside coverage | Install only when ready, inside coverage |
| Manual APN needed (e.g. some Japan SoftBank: vmobile.jp) | Install and set APN early; enable data when you connect after arrival |
Hong Kong and Malaysia pages often add: activate after arrival; if you install early, turn that eSIM’s mobile data off. See Hong Kong unlimited and Malaysia unlimited.
Checklist to avoid starting early
- Read activation / validity notes before checkout—carrier options can differ.
- Right after install: keep that eSIM’s mobile data off unless you intend to use it now.
- Dual SIM: keep OTP/calls on your home SIM; put data on the travel eSIM (Data-only vs calling).
- For roaming plans: turn on data roaming only after landing.
- Complete APN or dial codes (e.g. Mobifone 900 → 1) before speed tests.
- Plan top-ups before you run out of days or data.
Myths
“Scanning the QR always starts the days.”
Not always—many plans start on connect + data. Download-start plans do start on add/download.
“Installing early is always safe if I have not landed.”
No—if that line connects, or the plan starts on install, the clock can run early. Some number plans can also fail if installed outside coverage.
“Installed means activated.”
No—you still need to enable the line, switch data, and sometimes roaming / APN / dial codes.
“Every eSIM for a country uses the same rule.”
No—e.g. Vietnam Vinaphone (often connect-start) vs Viettel / Mobifone (download-start) can sit on related product lines.
Bottom line
- Install adds the profile; activate turns the line on and connects.
- Jeko’s default is usually install early, activate after landing—but confirm connect-start vs download/install-start.
- For high-risk options (Truemove H local number, Viettel, Mobifone, etc.), install only when ready and follow coverage / dial / deadline notes.
Browse the full catalog or popular destinations: Japan, Korea, Thailand, Vietnam. More help: FAQ.
