The onesim blog
Good trips start here.
Places to explore, practical travel advice, and ideas for your next journey.
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20 articles
Travel tips
Offline maps done properly, and the backup for when they fail
Downloading a map is thirty seconds of work that removes most of the ways a travel day goes wrong. Here is how to do it on both platforms, and what offline maps still cannot do.
Destination guides
48 hours in Istanbul, and one ferry you should not skip
Two days across two continents: what the headline sights cost now, how İstanbulkart works, and why the €1 commuter ferry beats every organised cruise.
Destination guides
Vietnam north to south in two weeks
Hanoi to the Mekong by train and short flights — the 90-day e-visa, the two climates running at once, and the bay worth avoiding the crowds on.
Travel tips
How much mobile data do you actually need abroad?
Real megabyte-per-hour figures for maps, messaging, social feeds and video — and why most travellers buy two or three times more data than they use.
Travel tips
eSIM, roaming or a local SIM: what each one really costs in 2026
An honest comparison of the three ways to get online abroad — including when roaming is the right answer and when a local SIM still wins.
Travel tips
Preparing your phone before an international trip
A short checklist for the week before you fly: compatibility, data, maps, banking and the settings that stop roaming surprises.
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