We all know that even traditional SIM cards—yes, including those with EU “Roam Like at Home” plans—often lose connection briefly at borders. That’s usually because the phone needs time to disconnect from one country’s network and latch onto another. And in those remote, in-between zones, coverage from either side can be patchy or delayed. It sounded like the perfect plan: hop on a train in Vienna, cross into Slovakia, and eventually roll into Budapest, all while testing the limits of modern travel tech—specifically, an eSIM. eSIM border crossing

No SIM swaps. No hunting down mobile shops. Just digital connectivity flowing seamlessly across borders. Or so I hoped. eSIM border crossing

Spoiler alert: it wasn’t entirely seamless. But it was close—and that in itself tells a lot about how far eSIMs have come (and where they still stumble).

The Setup: One Train, Three Countries, One eSIM border crossing

To make this as real-world as possible, I used a mid-range Android phone with dual SIM capabilities and activated a popular travel eSIM that promised multi-country coverage across Europe. The plan? 5GB of data valid across Austria, Slovakia, and Hungary. The ride? A standard EuroCity train that leaves from Vienna Hauptbahnhof, stops in Bratislava, and ends in Budapest’s Keleti Station. Time to find out whether eSIMs can keep up when the wheels start rolling and the borders start blurring.

Austria: The Comfort Zone

Leaving Vienna, the eSIM connected quickly to one of the local carriers—A1. Speed was decent, somewhere between 20-30 Mbps. Social media scrolled smoothly, and I managed to join a Google Meet call with only a few hiccups in video quality. Nothing major. If you didn’t know you were on an eSIM, you wouldn’t think twice.

That’s the thing with eSIMs in your home or first country: they behave like regular SIMs. But the real question isn’t how well they perform before a border. It’s what happens when you cross one.

Border Hiccup #1: Austria → Slovakia

As the train rolled past Bruck an der Leitha and crept toward the Austrian-Slovakian border, I kept one eye on the countryside and another on the signal bars.

At about 10 minutes from the border, speeds started to dip—YouTube struggled to buffer, and Google Maps took a few seconds longer than usual to update my location. Then, just before the border, I lost signal completely.

Blackout.

To be fair, the train was in a rural stretch of farmland, so physical infrastructure likely played a role. But here’s the key part: the eSIM didn’t auto-switch to a Slovakian carrier until about 6 minutes after we were clearly in Slovakia.

I had to toggle airplane mode off and on to nudge it into action.

That’s one of the weaknesses of eSIMs—while they can auto-switch between partner networks, they’re not always aggressive about it. Physical SIMs sometimes behave the same way, but with eSIMs, you don’t get that comforting “pop” when switching networks. It’s all in the background, and sometimes that means it stays stuck longer than you’d like.

Once connected to Slovak Telekom, everything bounced back. I ran a speed test: 17 Mbps down, 5 Mbps up. Not bad, though latency hovered around 120ms—noticeably higher than in Austria.

Apps that rely on instant location updates (think Uber, Google Maps with live train data) were noticeably sluggish. But for browsing, messaging, and social media, everything felt normal again.

Slovakia → Hungary: The Mid-Journey Gamble

After a quick stop in Bratislava, the train picked up speed toward the Hungarian border. This stretch was smoother, surprisingly.

Maybe it was timing, maybe better tower placement—but the eSIM handled the switch to Magyar Telekom more gracefully. No total signal loss this time, just a brief dip in data speed for a couple of minutes.

Here’s where things got interesting: while the switch between Slovakia and Hungary was technically seamless, I could tell the eSIM took a few seconds to “wake up” fully. At first, speeds were slow (3-5 Mbps), but then surged to around 25 Mbps once the connection settled.

It reminded me of waking up your laptop from sleep—it works, but it’s groggy at first.

What About Latency?

Latency was the biggest inconsistency throughout the trip. In Austria, pings were around 40ms. In Slovakia, it jumped to 120ms. In Hungary? It fluctuated between 60–100ms. If you’re just browsing, you won’t notice. But for video calls, gaming, or real-time translation apps, it makes a difference.

And yes, I did try a WhatsApp call mid-border crossing. Result? Patchy audio, frozen video, and an eventual drop. Once the eSIM stabilized in the new country, calls were fine again. So, no — not quite “meeting-ready” during the transition zone.

Final Stop: Budapest

By the time the train arrived in Budapest, the eSIM was running as smoothly as ever. No need to swap cards or buy local SIMs. That alone is a win. But I was left thinking: is this truly ready for flawless border-crossing usage?

In my opinion: almost. eSIM border crossing

What Worked Well

✅ No need to buy or swap SIMs in each country. One eSIM profile, one download, three countries.

✅ Post-border performance was reliable. Once the eSIM latched onto the new network, everything worked smoothly.

✅ Battery-friendly. Unlike some global SIMs that seem to constantly search for a signal, this setup was pretty stable (I got through the 5-hour ride on a single charge).

What Needs Work eSIM border crossing

❌ Auto-switching still feels passive. It often took longer than expected to connect to the new network, especially at the Austria–Slovakia border.

❌ Temporary signal dropouts at rural crossings. This might be a network coverage issue more than an eSIM issue, but it still affects the real-world experience.

❌ Latency spikes during border transitions. This is noticeable for voice/video calls and live apps.

Should You Use an eSIM for Train Travel Across Borders?

Absolutely. Despite its imperfections, using an eSIM on a multi-country train trip was far more convenient than carrying multiple SIMs or dealing with roaming costs. If your work depends on stable internet every single second, then you might need to keep a backup physical SIM. But for most travelers—digital nomads, tourists, casual business users—this is more than good enough.

My biggest advice? Learn to manually switch networks if needed (it’s just a few taps), and always download your eSIM before you hit the tracks. Also, having a second fallback SIM slot (or a Wi-Fi dongle) doesn’t hurt.

eSIM Used for This Trip: Europe eSIM at a Glance

For this trip, I used an eSIM from Europe eSIM, and overall, it held up well. What makes this provider stand out is its unlimited data plans across Europe, optional voice packages, and impressively broad country coverage—ideal for multi-national journeys like mine. Pricing is very competitive, especially compared to traditional roaming or buying separate SIMs in each country. Whether you’re a frequent traveler, digital nomad, or just hopping borders for a weekend, Europe eSIM offers a convenient, reliable, and cost-effective solution that simplifies staying connected on the go.

Final Thought: A Work in Progress Worth Embracing

eSIMs are changing how we travel. They’ve simplified what used to be a tedious part of border-hopping. Yes, the tech still has some gaps—especially when it comes to those quiet zones between countries where signals fade and networks pause for a second.

But overall? They’re 90% there. And that last 10%? It’s getting better every month.

If you’re ready for fewer SIM trays and more signal bars—even on a moving train—then yes: eSIMs are worth the ride. Just hold on tight during those border bumps.