Privacy

No location, no email, no trackers of our own.

What is stored

• A saved spot: the wallet address, its pin (computed from the address), the place name, and the postcards filed for it. This is public, like the blockchain it comes from.
• Sign-in: a one-time nonce and a signed session cookie (HttpOnly, 7 days). The signature is a message, never a transaction.
• Rate limits: a counter per IP address per minute, overwritten every window.

What is not

POSTCARD never asks for your location; the pin is a hash. Looking at an address without saving it stores nothing about you. Your browser fetches imagery straight from NASA GIBS and the Sentinel-2 bucket on AWS, and the weather from Open-Meteo, so those services see your IP address and the coordinates of the spot you are looking at. Cloudflare, which hosts the site, may count visits with its privacy-first Web Analytics.

In your browser

If you save a spot, its address is remembered in this browser so the site can tell you when new mail arrives. Clear the site's data to forget it.