eSIM for travel: the discreet digital passport

A consultant lands in Shanghai. His French carrier doesn’t connect to the local network. He enables roaming at $12/MB. Three days later, an $800 bill for sending PDFs. The $9 eSIM with 10GB was in his inbox the day before he left.

The common trap

“I’ll just enable roaming, it’ll work.” This is the default decision for the majority of business travelers. Roaming works — technically. It’s also among the most expensive, most exposed, and least discreet options available for staying connected abroad.

An eSIM changes the picture. It’s cheaper, faster on the native network, and structures your connectivity profile in ways that have concrete implications for both privacy and operational security.

How eSIM works

The traditional physical SIM is a removable card. An eSIM (embedded SIM) is a chip soldered directly into the device, physically non-removable. What changes is the carrier profile — the configuration that allows the device to authenticate on a mobile network — and that profile is now downloadable.

The process:

1. You buy a data eSIM plan from a provider (Airalo, Holafly, or directly from the local carrier)
2. You receive a QR code by email or in the app
3. You scan the QR code in the device settings
4. The eSIM profile downloads and activates — typically in under two minutes

Compatibility: iPhone XS (2018) and later, Pixel 3 and later, Galaxy S20 and later, most premium devices since 2020. Note: iPhones purchased outside the United States may have carrier unlock constraints, and some carriers lock the eSIM to their own network.

Multiple profiles: depending on the device, multiple eSIM profiles can coexist (between 5 and 8 on recent iPhones), but only one can be active at a time for data — except on dual-SIM active models that support simultaneous active SIMs.

Why it beats roaming

Cost first. A standard roaming plan can run anywhere from $5 to $20 per megabyte in some destinations outside the EU. Even “generous” roaming plans cap out at laughable data volumes or throttle after a few gigabytes. An Airalo eSIM for 10GB in Asia costs between $9 and $20 depending on the country. The gap is often a factor of 10 to 50.

Operational discretion. When you enable roaming, your home carrier (AT&T, Verizon, Vodafone, Orange) is informed in real time of your presence in the country, which networks you’re using, and potentially your aggregated traffic. With a local eSIM, your home carrier sees nothing of your local activity — it just knows you’re not using their network.

Network quality. On roaming, you’re using a partner network under a bilateral agreement, often with lower priority than local subscribers. With a local eSIM, you’re a direct (or near-direct) customer of the local network. Quality, latency, and priority are generally better.

Flexibility. You can keep your home line active in parallel for incoming calls and important SMS messages (notably MFA codes), while using the local eSIM for data.

Where to buy

Airalo: the most universal option. Coverage in 200+ countries, polished interface, app available on iOS and Android. Competitive prices. The privacy policy is reasonable — an email is required at registration, use an alias if discretion matters to you. Recommended as a starting point.

Saily (by NordVPN): good value for money, broad coverage. If you’re already a NordVPN subscriber, potential combined benefits. Clean interface.

Holafly: unlimited data model in select countries at a flat price. Convenient for long trips or destinations where you don’t want to monitor consumption. Read the “unlimited” conditions — there’s typically a daily throttling threshold after a certain volume.

Directly from the local carrier: best guaranteed network quality, sometimes cheaper, but usually requires identity verification with an official document. Practical in countries where carriers have functional apps (Japan, South Korea, Singapore). In China, passport registration is mandatory regardless of provider.

Avoid: eSIMs sold at airports, in physical shops, or through unvetted resellers. Prices are typically two to three times higher than Airalo, with no added benefit.

Security and privacy implications

Your IMEI remains visible. Whatever eSIM profile you use, your device identifies itself on the network with its IMEI — a unique hardware number. The local carrier sees this IMEI. If you need a complete dissociation between your usual identity and your connectivity on the ground, a dedicated device is necessary — not just a different eSIM.

The registration email. International eSIM providers (Airalo, Holafly) require an email address. If you want to limit traceability, use a disposable alias (SimpleLogin, AnonAddy) rather than your primary address. Most don’t require real identity verification beyond the email.

Countries with mandatory registration. In China, Russia, Saudi Arabia, Pakistan, and many other countries, obtaining a local SIM or eSIM requires identity verification with an official document. This data enters the local state’s records. That’s not necessarily a problem — it’s a fact to integrate into your threat model.

Your primary line as a tracking vector. Even if you’re using a local eSIM for data, if your home line is active on roaming in parallel, your home carrier knows you’re in that country. Depending on your threat model, it may be preferable to disable roaming entirely on the primary line and rely exclusively on the local eSIM.

Multi-eSIM as an operational strategy

For frequent travelers or sensitive missions, multi-eSIM management becomes a strategy in its own right.

Permanent profile: your primary professional line, always present in the device, sometimes in airplane mode or with data disabled depending on context.

Local profile per destination: an Airalo or equivalent profile purchased before each departure. Local data, no roaming, no visibility for the home carrier.

Use-case separation: on dual active eSIM devices (US iPhone 14+, select Android), you can configure the local eSIM for data and the primary line for calls and SMS. Your contact sees your regular number. Your data traffic runs on the local network.

Before departure: what to do

Buy and download the eSIM profile before you arrive. Downloading an eSIM profile requires an internet connection — ideally on trusted Wi-Fi, at home or at the office. Avoid activating at the airport on public Wi-Fi or via in-flight roaming (expensive and potentially uncontrolled).

Test activation before the day of travel. Some profiles require the device to be carrier-unlocked, or require “eSIM support” to be enabled by your current carrier. Check this several days before departure, not the night before.

Sort out your MFA. Identify accounts that send codes via SMS to your primary number and decide how you’ll handle them on location.

Disable automatic roaming once the local eSIM is active. Some devices automatically fall back to roaming if the local eSIM signal is weak. This behavior can generate unexpected charges.

• N1 Verify eSIM compatibility of your device before departure
• N1 Subscribe to an Airalo (or equivalent) plan before departure, on trusted Wi-Fi
• N1 Download and activate the eSIM profile before arriving at the destination
• N2 Use a disposable email alias for eSIM provider registration
• N2 Disable automatic roaming on the primary line once the local eSIM is active
• N2 Keep the primary line active only for critical SMS MFA codes
• N2 Check local registration requirements (identity documents) in mandatory-registration countries
• N3 For sensitive missions: fully disable the primary line, use the local eSIM exclusively
• N3 For high-discretion profiles: dedicated device with eSIM purchased without link to your usual identity