Planning to switch carriers or grab a cheap eSIM plan? Before you buy, check two things: whether your phone is unlocked and whether it supports eSIM. This guide walks you through both in plain English, with quick checks for iPhone and Android.

An eSIM is a tiny, rewritable chip already built into your phone that lets you activate mobile data plans instantly, no plastic SIM card, no shop, no waiting. It’s perfect for travel: buy a local/regional plan online, scan a QR code (or tap “Install” in the app), and you’re connected the minute you land. If you’re hunting for bargains, most eSIM brands run promo codes, use them at checkout to shave 10–50% off your data.