KAI-Pay
Wallet

BITCOIN / LIGHTNING / YOUR EVERYDAY WALLET

Public beta – use it in your browser

Pay with Bitcoin. Simple and self-custodial.

KAI-Pay is a Lightning wallet for web and mobile. Send, receive and accept payments at the counter. Your keys stay with you, not with us.

Installation and app availability · KAI Oracle: evidence and network data

Open the wallet Open point of sale

Beta: best start with small amounts. Read first: Risk warnings · Terms of use

Illustration – no real wallet data
Self-custodialNo registrationPublic beta
00 / KAI EXPLAINS

One coffee, two screens.

How a payment with KAI-Pay works – from the customer’s side, from the till’s side and behind the scenes. No prior knowledge needed.

Point of view
Simulation with example values – no real money, no real QR code. The length of the animation is no promise for real payments.
KAI
  • Nothing happening yet. Exactly as planned.
  • No PIN pad. No card slot. Just a square.
  • One look at the amount. Then go.
  • No bank. No closing time. No hold music.
  • Coffee understood. Blockchain lecture skipped.
  • Price in. Invoice out.
  • Your shop. Your invoice. Your money.
  • Customer’s turn now. Deep breath.
  • No payment provider in between. Me neither, by the way.
  • Green means paid. Before that means: wait.
  • 1 sat = 0.00000001 bitcoin. Tiny, but real.
  • Signed and with an expiry date. Bureaucracy – just fast.
  • Your key stays with you. Even from me.
  • No storage on the way. The money never sits anywhere.
  • Receipt in. Payment final.
Steps
  1. Amount The shop types in the price: €3.50 for a coffee. Nothing happens on your side yet.
  2. QR code The till shows a QR code. That’s the invoice. You scan it with your wallet.
  3. Check Your wallet shows the amount, the fee and the total. Only when everything is right do you tap “Confirm and send”.
  4. On its way The payment travels over the Lightning network to the till, usually within a few seconds.
  5. Paid Your wallet shows “Sent”, the till shows “Paid”. The coffee is yours.
  1. Amount You type in €3.50 or tap the item, then choose “Charge”.
  2. QR code The till shows the invoice as a QR code. Your customer scans it with any Lightning wallet.
  3. Check The customer checks and confirms on their phone. Meanwhile your till shows “Waiting for payment …”.
  4. On its way The money goes straight into your own wallet. Nobody holds it in between.
  5. Paid The till shows “Paid” and a numbered payment receipt. Only now do you hand over the coffee.
  1. Amount Bitcoin is the money; amounts are counted in sats: 1 bitcoin is 100 million sats. The till converts the €3.50 into sats at the current rate and records the rate.
  2. QR code The code contains a Lightning invoice: amount, recipient and expiry time, digitally signed. Once it has expired, it can no longer be paid.
  3. Check Your wallet signs the payment with your key. The key is created on your phone and is never sent to KAI-Pay.
  4. On its way Lightning passes the payment along via network nodes, with no bank in between. KAI-Pay holds no money along the way.
  5. Paid As a receipt, your wallet gets a secret code that only exists in exchange for payment. That makes the payment provable and final: there are no chargebacks like with cards.
01 / EVERYDAY BITCOIN

What you do with KAI-Pay

Seven ways to use KAI-Pay – each in a few steps, with clear costs before you confirm.

Send money

Scan a QR code or paste an address, check amount, fee and total, confirm. Lightning payments usually take only seconds. Also as a standing order with a reminder – nothing is paid until you confirm.

Core

Request a payment

Enter amount and purpose, share a QR code or link. You see in the app when the money has arrived.

Core

Accept payments at the counter

Type the amount or tap articles, the customer scans, the payment is confirmed – on a separate till device or directly on your phone. Amounts in EUR, USD, GBP, CHF, CAD, AUD or JPY, receipts as PDF. Staff devices can collect but never send money. Daily and monthly closing with CSV export and refunds in the wallet. Point-of-sale guide Benefits & explanation →

Available

Pay L402 services

Pay access invoices of services (L402) via Lightning. The wallet checks that invoice and access belong together and then shows the access proof. Benefits & explanation →

Connect a service

Payment link and ready-made button for your shop or website – optionally with a signed notification to your shop for every payment. Set up right in the wallet. Benefits & explanation →

Beta

Manage AI budgets

AI assistants may only propose payments – to recipients you allow, up to your daily and monthly budget. You confirm every payment. With a test assistant to try it out. Benefits & explanation →

Beta

Reserve on BitBox

Large amounts safe on your BitBox, everyday money in KAI-Pay. Surplus funds only go to addresses your BitBox verifies itself – with the cost in percent before you send. Benefits & explanation →

Beta
02 / YOUR KEYS, YOUR CONTROL

Self-custodial – what does that mean?

With KAI-Pay, your money is yours. That has three consequences you should know.

  1. Your keys stay with youThey are created on your device and are never transmitted to KAI-Pay. KAI-Pay cannot move your money.
  2. Your 12 words are the backupThey restore your wallet on another device. Write them on paper and keep them safe.
  3. Nobody can recover it for youNot even us. If you lose both device and words (for a passkey wallet, also the passkey), the funds are lost. That is the price of real self-custody.

Technology: KAI-Pay uses the Lightning Network and Spark via the open-source Breez SDK. Spark needs the Spark operators to cooperate for payments. For emergencies, Spark provides a unilateral exit to the Bitcoin blockchain – subject to conditions we explain openly in the risk warnings.

03 / BUILT ON TRUST

Security and privacy

No account, no password

You do not create an account with us. We hold neither your keys nor your funds.

No trackers from KAI-Pay

KAI-Pay itself uses no cookies, no analytics or advertising trackers and no fonts from third-party servers. Payment networks and connected services receive what they need for payments and for running the wallet, some of them on every start; details in the privacy policy.

Protection against double payments

Every payment carries a unique identifier, and the app never sends a second time on its own. If the outcome is unclear, it warns you before another payment. This does not protect two devices with the same wallet against each other.

Emergency package for exit

Save your wallet’s exit data as an encrypted file. It is meant for the unilateral exit without the Spark operators; that costs on-chain fees and has not yet been tried in practice. Your 12 words provably open the wallet without Breez software as well (with Lightspark’s Spark SDK).

Private mode and “Who sees what?”

Private mode is on by default. In the wallet, “Who sees what?” shows which service sees which data – even before you create a wallet. Encryption does not mean anonymity.

Unlock with your fingerprint

Unlock with your fingerprint instead of the PIN. In the browser you can remove the PIN fallback – then the wallet on the device can no longer be attacked offline. Your 12 words remain the backup.

04 / GOOD TO KNOW

Frequently asked questions

When can I use KAI-Pay?

Now: KAI-Pay runs as a public beta in your browser at app.kai-pay.net and can be installed there like an app. For Android there is so far only a test version, not in the Play Store; store apps for Android and iOS will follow later.

What does KAI-Pay cost?

We charge no fee for the wallet. Payments may incur third-party fees; when sending, you see them before you confirm.

Can I buy Bitcoin with KAI-Pay?

Not from KAI-Pay itself. Under “Buy bitcoin”, the wallet opens the external website of Strike; the provider of the purchase there is Zap (Strike) Europe Limited, a crypto-asset service provider from Malta authorised under MiCA. KAI-Pay does not accept your purchase order, does not process the purchase and receives no remuneration for the link. Account, identity check, costs and payout are governed by Strike’s terms. The purchase is not anonymous. More

What happens if KAI-Pay disappears?

Your keys are not held by us. Your 12 words can restore the wallet with other software based on the Breez SDK as long as the Spark operators cooperate. More in the FAQ.

Do I need an account or my email address?

No. The wallet is created on your device, without registration.