Free phone push notifications for onchain events with ntfy (no account)

Send blockchain alerts (wallet transfers, approvals, contract events) to your phone for free using ntfy.sh topics. No app account, no Telegram bot, no Discord server.

ntfy is an open-source pub/sub push service. You POST text to https://ntfy.sh/<topic> and every phone subscribed to that topic gets a notification. There is no signup. The topic name is the only secret, so use something long and random.

Steps

1. Install ntfy (Android: Play Store or F-Droid; iOS: App Store).
2. Generate a topic, for example openssl rand -hex 16, and subscribe to it in the app.
3. Test it: curl -d "hello" https://ntfy.sh/<topic>.
4. Use https://ntfy.sh/<topic> as the webhook in any tool that can POST text.

Doing it with Ledgerbell (free tier)

1. Open the Ledgerbell dashboard and click Create a new key (no signup, no email; save the key).
2. Pick the chain (Base, Ethereum, Arbitrum One or OP Mainnet), type Wallet, paste the address.
3. Paste a webhook URL (Discord, Slack, Telegram bot, ntfy or any JSON endpoint) and click Add watch. Use test to send a sample message.

Free: 3 watches and 50 alerts/day, polled about once a minute. Pro (30 watches, 1,000 alerts/day) is 5 USDC on Base per 30 days. Or use the API:

curl -s -X POST https://ledgerbell.quietworklabs.workers.dev/api/key
curl -s -X POST https://ledgerbell.quietworklabs.workers.dev/api/watch -H 'content-type: application/json' -H 'x-api-key: lb_...' \
  -d '{"chain":"base","kind":"wallet","address":"0x...","webhook":"https://ntfy.sh/your-long-random-topic"}'

Self-hosted ntfy servers also work: any host starting with ntfy. is sent as plain text with a title.