Hotspot_Hopper
Appearance
Colours for the whole app.
The Hotspot_Hopper title and headings. "Default" follows the body font.
Everything else.
A Google Fonts family name (e.g. Press Start 2P) or a link to a .ttf / .otf / .woff2 file. Pick "Custom" in a menu above to use it.
Saved to your account, so it follows you wherever you sign in.
Treasure chest
Receive sats from any Cashu ecash wallet. Sats for this account are stored in your browser but can be moved to any external Cashu wallet.
Pixel treasure you hold. Tap one to stash it at this hotspot, send it to a friend, or lock it to a blank NFC tag.
This item now lives on a tag. Write this URL to a blank NFC tag (or print the QR); whoever taps it can move the item into their chest.
Divide 100 points between them.
Scan a QR code
Point the camera at a friend's QR code to add them, or at a hotspot's code to open it.
Hotspots near me
Finds public hotspots whose last reported location is close to you. Private hotspots never show up here.
FAQ
What is Hotspot_Hopper?
A hotspot is a physical NFC tag that moves. Tap the tag to open its page, sign in with your own key, and read or leave messages there.
Found it? Hide it somewhere new, capture the GPS location, and leave a clue. The tag posts where it went and messages everyone who follows it. Anyone with the link can see the last known location and clue; only people who tap the tag can read and post messages.
A tag does not have to be a travelling game. It can mark a lost item so a finder can message you, hold emergency medical details, or lock a creature or object that only a tapper can claim.
How do I make my own hotspot?
Press the + icon and choose Make hotspot. Give it a name and a description, pick its type, and choose whether it is public (findable with "hotspots near me") or private (reachable only by the link or the tag itself). You can be named as the creator or stay anonymous.
Then set a password. The hotspot's key travels on the tag encrypted with it, and anyone who taps gets that encrypted key, so make it long. The password is what unlocks Hotspot settings later.
You will get a tag URL. On Android, Write tag puts it straight onto a blank NFC tag. Anywhere else, copy the URL and write it with any NFC writer app as a URL record — or skip the tag entirely and print the QR code, which opens the hotspot exactly like a tap.
A blank hotspot is the exception: it has no password and no key on the tag. Whoever taps it first names it, picks its type and sets the password.
What is a private key?
Your private key is your account. It is a long secret number, written starting with "nsec", and holding it is the only thing that proves you are you. There is no username, no password reset and no company holding it for you.
From it comes your public key, written starting with "npub". That one is safe to share — it is how people follow you and address messages to you.
New Key makes one. Save Key writes it to a file on your device, locked with a password you choose. Keep that file somewhere you will still have it later: if you lose the key, the account and everything signed with it is gone, and if someone else gets it they are you. Never paste your nsec into a site you do not trust — this one keeps it in your browser and never sends it anywhere.
What are sats?
A sat, short for satoshi, is the smallest unit of bitcoin: one hundred-millionth of one. Prices in tiny amounts are easier to read in sats than in decimals of a bitcoin. Tap the balance to switch between sats and ₿.
The treasure chest holds sats as Cashu ecash — tokens from a mint you pick in Settings. They live on this device like cash in a pocket, so back them up the way you would a wallet. You can zap a message, leave sats at a hotspot for whoever finds it next, or send them to a friend.
What is Nostr?
Nostr is the open protocol this app is built on. Instead of an account on one company's server, you have a key, and you publish messages signed with it to relays — small servers that anyone can run. Any relay can carry anything, so no single one can shut you out.
That is why your key works everywhere. Sign into any other Nostr app with it and your profile, follows and followers come along. Hotspots are ordinary Nostr events too, so they outlive this app.
How do I self-host a private Hotspot_Hopper relay?
Run any Nostr relay — strfry and nostr-rs-relay are the usual choices, both free and happy on a Raspberry Pi. Give it a domain with TLS so it answers on wss://, and use the relay's own allow-list settings if you want only your own keys writing to it.
Hotspot_Hopper has no relay picker yet: its list lives in DEFAULT_RELAYS at the top of nostr.js. To run everything through your own relay, edit that list and publish your own copy of the site, then point your tags at it. Because the app is static and every event is signed by you, your copy talks to the same hotspots as anyone else's.
Keep at least one public relay in the list unless you mean to be unreachable — people outside your relay cannot see your hotspots or send you messages otherwise.
How do I buy pre-made tags?
There is no official shop yet. Any blank NFC tag works as long as it holds a URL record and is NTAG215 or larger — the smaller NTAG213 runs out of room for longer tag URLs. Stickers, discs, keyfobs and waterproof tags are sold by plenty of suppliers online.
Write it yourself in one step: make the hotspot, then press Write tag on Android, or copy the URL into any NFC writer app. If you would rather have tags arrive ready to tap, use the Message button at the bottom of the page to ask.
How do I support development?
Press Support at the bottom of the page to send a zap over Lightning — any amount, and it goes straight to the developer with nothing in between. Follow and Message are down there too, and honest feedback about what broke is worth as much as sats.
The app is free, has no accounts, no tracking and no company behind it. Putting tags out in the world where people will find them is its own kind of support.
Profile
People you follow in Hotspot_Hopper. Tap a name to see their hotspots and friends.
Private messages with anyone on Nostr — they work with Amethyst, Damus, 0xchat, Primal and other apps too.
Settings
Account
Public: anyone viewing your profile sees the hotspots you follow. Private: only the npubs you give permission to can.
Treasure chest
Sats live at the mint that issued them. Add as many mints as you like; the active one is used for sending, stashing and zaps. Tokens you receive are kept at their own mint.
Hotspot settings
Open this page from the tag to unlock its settings — the tag carries the hotspot's key.
This tag carries the hotspot's key. Unlock it to name the hotspot, rewrite the tag, issue a new reader key, or refresh its page.
Public: findable with "hotspots near me". Private: only by link or tag. Takes effect from the next recorded location.
Only people who tap the tag can read these. They are encrypted to the tag's reader key.
Removes its profile, site and location history from the relays and takes the tag out of "hotspots near me". Messages people have already decrypted stay with them. This cannot be undone.
Create a new hotspot
Makes a fresh hotspot identity and publishes its site. You get a tag URL to write to an NFC tag; anyone who taps it lands on that hotspot.
You are not signed in — that is fine, the hotspot gets its own key. Sign in first only if you want to lock a creature or item from your chest to it, or to be reachable as a lost item's owner.
Public hotspots can be found with "hotspots near me". Private ones are only reachable by sharing the link or finding the tag.
Your npub is named as the creator, and you sign a matching claim — visitors who follow you see the hotspot is really yours. Anonymous publishes neither, and nothing links the hotspot to you.
The hotspot's key goes on the tag, protected by this password. Anyone who taps the tag gets the encrypted key, so use a long password.
A blank tag has no password yet, and its key is never written to the tag. Whoever taps it first names it, picks its type and sets a password — the tag is not touched again.
Its key comes from your own key, so you can always get this hotspot back with "Recover my hotspots" below — even the anonymous ones.
Hotspot created. Write this URL to an NFC tag (as a URL record):
Or print this QR code instead of using an NFC tag — scanning it opens the hotspot exactly like a tap:
Save this URL somewhere safe too — it is the only copy of the hotspot's key.
Recover my hotspots
Hotspots you make are derived from your own key, so signing in is enough to get them back — no key file, no tag URL. Nothing is sent anywhere: the keys are worked out on this device and only their public halves are looked up.
Profile
✉ A friend left you something
Save your private key if you want to reuse this account to follow hotspots, add friends, and collect treasure. If you use your key in other NOSTR apps, your follows, followers, and messages will come along for the ride.
⬜ Set up this hotspot
This tag is blank. Give it a name, choose what kind of hotspot it becomes and set its password. The tag itself stays as it is — nothing needs rewriting.
Public hotspots can be found with "hotspots near me". Private ones are only reachable by sharing the link or finding the tag.
The hotspot's key goes on the tag, protected by this password. Anyone who taps the tag gets the encrypted key, so use a long password.
Done — nothing to write. The tag already points here, and your password now opens its settings.
Hotspot
Last known location
Tap tag to read and write messages
Messages at this hotspot can only be opened by tapping the physical tag — this page was opened without it. The last known location and clue are shown above; go there, tap the tag, and sign in to read or leave a message.
Hold the tag against the back of the phone — the page picks it up without reloading.
On iPhone, hold the tag to the top of the phone: it reopens this page with the tag's key. Turn on "Stay signed in on this device" in Profile so you don't have to sign in again.
Hotspot deleted
The owner has deleted this hotspot. Its tag no longer leads anywhere.
No hotspot
This page isn't attached to a hotspot. Tap a hotspot tag to open, read or post messages. Sign in or create an account, then tap + if you want to create a new hotspot.
Leave a message
A fresh key has been created for you to post with. Save the key if you want to enable reusing this account, following hotspots, adding friends and accessing your treasure chest.
If you use your key to sign into any other app built on NOSTR, your profile, follows, followers, and messages will come along for the ride.
Pick a password to protect your key. It encrypts the key file you are about to download — without the password that file is useless, and there is no way to recover it, so keep both somewhere safe.
Sign in
Create a new key if you want a fresh account. Save the key if you want to be able to reuse the account.
Protect the key file with a password. Without it the file is useless — there is no recovery.
Remote signer (Amber, nsec.app, bunker)
Your key stays in the signer app. Hotspot_Hopper asks it to sign and decrypt for you, so expect approval prompts there the first time.
Open this in your signer app, then come back here:
Hotspot messages
You found an item
Leave a message
Anyone who taps the tag can decrypt and read this message
Moved the tag? Give it a fresh reader key so people who found the old spot can't keep reading. Write this URL to the tag when you hide it.
Treasure
Save your key or sign in to collect or leave treasure.
Leave an item from your chest here for the next finder, or grab what's been left. First tapper to claim keeps it.
Tag trail
Where the tag has been. Tap a stop to see the messages left while it was there.
Hotspots you follow
Tap a hotspot to see where it was last reported. The counter shows messages from that tag you haven't opened yet.