Similar here. I use the app since it doesn't do anything invasive, but I also have a paper backup (I don't always carry it) because it's a bit too important to be dependent on a phone only. I bet I'd first find out about my certificate being revoked at some check point where my phone isn't working and I can't easily get a new one...

well, print it again then.

I know this, but a lot of people may not know because they don't care to read HN. Then they try to board a plane and get rejected.

to be fair, yes, you are right, it is going to be a pain for a lot of people.

> not installing any third party apps on my phone

Just out of curiosity, is that for privacy reasons or ? Seems rather strange for a smartphone ?

Can't you keep it in a jpeg file and show that?

You can do both. In addition to these two methods I also have a print of that QR code in my car.

In general? Or just COVID apps?