# Validity period

> A validity period is the length of time a prepaid eSIM or data plan stays usable, usually counted in days from activation or first connection to a network.

Source: https://viasimo.com/glossary/validity-period/
Also known as: plan validity, expiry period, plan duration

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A validity period is the length of time a prepaid eSIM or data plan stays usable, usually counted in days from activation or first connection to a network. When the period ends, the plan expires even if data is left over.

Every prepaid travel plan has two limits: a data allowance and a validity period, and the plan ends when you hit either one. A 30-day plan with a large allowance can expire with most of its data untouched; conversely, a heavy user can drain the allowance in the first week of a 30-day window. Understanding which limit you are likely to hit first is the key to buying well.

The detail that trips travellers up is when the clock starts. Policies differ: some plans activate at purchase, some when the [eSIM profile](/glossary/esim-profile/) is installed, and most travel eSIMs when the phone first connects to a supported network at the destination. Under the most common model you can safely install the eSIM at home days before departure, and the validity only begins when you land and connect. Always check the specific plan's terms, because installing early on an install-activated plan silently burns days.

Other points worth knowing: unused data is normally lost at expiry rather than refunded; many plans can be topped up or extended before they lapse; and validity is counted in calendar days, so a plan activated at 11 pm loses its first day almost immediately.

Concrete example: you buy a 15-day plan for France, install it at home on Monday, fly on Friday and connect in Paris that evening. The validity runs from Friday, so the plan covers your full two-week stay in [France](/destinations/france/).

For the practical steps, see [how to install and activate an eSIM](/magazine/how-to-install-and-activate-an-esim/); for matching plan length and size to your trip, start with [how much data you need](/magazine/how-much-data-do-i-need-for-travel/); and for trips longer than a month, read our [long-term travel connectivity guide](/magazine/long-term-travel-connectivity-guide/).