eSim - can I buy before I leave Canada?

You can certainly buy your eSIM before leaving. Be careful, though; some eSIMs activate upon purchase rather than allowing you to activate at your own schedule. I've suggested Nomad as an option, and they do things the right way. MobiMatters did not when I ordered an eSIM from them. Others here like Airalo, though I don't have personal experience with their products.

The ideal way to activate an eSIM is to find wifi upon landing in Europe and then follow the activation instructions. Activation will require internet access.

The Airalo sims we have had in France and UK were installed before we left from the US, then when we connected upon landing, it activated and started our time frame. When you click on the package you are interested in, it will say what the activation policy is, ours said "The validity period starts when the eSIM connects to any supported network/s." You do need internet access to install it, so it was easiest and less stressful for us to install before leaving home on our own wifi, rather than trying to get a good enough wifi connection in the airport after landing.

I have an Airalo reference code that saves you $3USD, if you are interested. others probably do too.

Exactly what bethb said. I used Airolo for 1 month plus in Spain this Spring. Totally worth it.
If you dont have a what’s app account, I suggest getting one, everyone uses What’s app in Europe.
Read the insctructions and follow them. Once you land, select you esim and it will activate automatically.
Better to download and install prior,, since you will be jetlag and going through customs etc.

added to what Martine said about Whatsapp -- be sure to sign up for WhatsApp before leaving your home country. You need to get a text message I think to complete the sign up, since it's tied to your local phone number. So must activate while on your regular sim. But only need data after that, regardless of location!

Another thumbs up for AirAlo. Depending on where you are traveling you can get a country specific, a region specific, or an international eSim. The first time we went to Spain my wife had a Spain specific eSim and I had an EU eSim. Last month she had an EU eSim and I had an international one (helpful when in Gibraltar and in Morocco).

Another plug for WhatsApp. Lots of people and businesses on whatsapp in the EU.

Also, if need be one can make free toll free calls at least to the US via Skype--helpful when one needs to call a US based business like credit card companies or airlines to sort things out.

Unlike other eSim vendors, Airalo does not include a voice number or voice service--not a big deal. Seems like even at home the phone is used 99% of the time for non-voice communication.

If one is paranoid one can install the eSim after one receives it and wait until one is in country to turn the travel eSim on. The eSims from Airalo will activate once the phone starts communicating with cell towers in that assigned country, or region--international ones obviously will go live once the esim is toggled on.

I think the Airalo website has a decent tutorial on how to make changes on your phone to avoid getting nailed by your primary carrier for international service (or not having service at all).

So the installation of the eSim and the toggling on the phone settings is independent of activation.

We chose to get 2-3 GB each for 30 days and didn't get close to using all of it--pretty easy to top up if needed though.

I'm not understanding the directive to enroll a WhatsApp account in the US before traveling. Not a bad idea, of course, but I had no issues enrolling after my arrival in Spain.

Signing up for WhatsApp before one leaves is one less thing to worry about when traveling. Last year I communicated with a relative and an AirBnB host via WhatsApp while waiting for luggage to come off of the carousel. Prior to our travels last month I communicated with most of our AirBnB hosts while still in the US. Don't need to wait to travel to install and use WhatsApp. Can message and call other folks on WhatsApp in the US. Amazed how much more popular WhatsApp is in Europe than here in the US.

Some people can’t receive texts to there number once the regular sim is turned off. If installing WhatsApp after the fact, it may want to verify by sending a text to your number, which you won’t get if your regular sim is off. This is the benefit of installing beforehand, all verification done and you can just proceed with using the app.

I’ve installed Airalo eSIMs on this side of the pond and then turned them on once I’ve got to my destination.

Yes - the benefit is that you can receive a text on your regular home number to set up your account. This number is then your id on WHatsapp - that will be the number that is then registered for Whatsapp and follows you across devices or whatever in the future. So it's also slightly easier for your regular contacts back home that still want to text/call you.