alt Hacker NewsWait, the balance is stored on the card? I'm fairly sure the balance is shown in the JR app too, so presumably that cannot be the case. [Update: or maybe not? I opened the app now and it's asking me to enable NFC and hold it up to the card.]
Anyway I love my Suica. I got it a good decade or more ago, I have a few thousand yen on there, and it's always ready for me when I go back to Japan. Useful on the Metro, trains and in shops. Easy to top up at the plentiful, dedicated top up machines. I also loaded Shinkansen tickets on it last time and travelled "ticketless".
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Op mentions that server side sync occurs outside of 200ms card/reader interaction.
I'm fairly sure the balance is shown in the app too
Can confirm that Suica shows the balance in Apple Wallet.
Yes, they do store the value. There was a blogpost posted to HN last year that discusses the cryptographic features of these cards [1,2]. It's amazing that these cards are almost solving the problem of secure digital money.
[1] https://news.ycombinator.com/item?id=43993711
[2] working link since original blog is down https://web.archive.org/web/20250517082035/https://aruarian....