Haudi Crypto, Inc.
Contents
- Introduction
- Requirements
- Connecting a wallet
- Checking balances
- Manage tokens & networks
- Sending
- Loading a payment from a QR code
- Switching accounts
- History and CSV export
- dApp integration (extension only)
- Security
- Troubleshooting
- Specifications
- Contact
1. Introduction
Openloop Pay is a mini wallet that makes stablecoins easy to use. You can check balances and send crypto assets. It runs as a browser extension on your desktop and as a web app on your smartphone.
Supported tokens and networks are EVM only (Ethereum and EVM-compatible chains). Alongside the built-in stablecoins (JPYC / USDC / USDT), you can add other EVM tokens. See §13 “Specifications” for the full list.
Your private keys stay inside your Openloop hardware wallet (or the wallet you connect); Openloop Pay never stores or accesses them (non-custodial).
Openloop Pay is a companion wallet that holds no keys of its own. The wallet itself (your keys) lives in your Openloop device or the wallet you connect over WalletConnect; Openloop Pay only shows balances and relays transactions for signing. So, unlike wallets that keep an (encrypted) key in the browser, even if the web app or extension were compromised, there are no secrets inside to steal.
1.1 Key features
| Feature | Description |
|---|---|
| Wallet connection | Connect Openloop over USB / Bluetooth, or connect a supported wallet via WalletConnect |
| Balances | View your token balances and your gas (fee) assets |
| Manage tokens & networks | Choose which token × network to show and send; add and remove them |
| Sending | Enter a recipient and amount, then approve with the connected wallet |
| QR scanning | Read a payment-request QR code to pre-fill the send form |
| History | Review send history and export it as CSV |
| dApp integration (extension only) | Connect to dApps in your browser and approve requested signatures on your Openloop device |
1.2 What you can connect
- Openloop hardware wallet — over USB on a desktop, or Bluetooth on a smartphone. You review and approve signing on the Openloop device itself.
- WalletConnect-compatible wallets — Openloop Connect and other WalletConnect-compatible wallets.
- dApps (browser extension only) — decentralized apps on the web can request signatures through Openloop Pay. See §10.
2. Requirements
Openloop Pay ships in two forms: a browser extension
(Chrome/Edge only) and a web app
(https://www.crypto.haudi.jp/openloop/pay/app/). Which
connection methods the web app can offer depends on the browser.
2.1 Web-app support matrix
| Environment | USB (WebHID) | Bluetooth (BLE) | Safari-extension bridge | WalletConnect |
|---|---|---|---|---|
| Desktop Chrome / Edge | ✓ | – | – | ✓ |
| Desktop Firefox | – | – | – | ✓ |
| Desktop Safari (macOS) | – | – | – | ✓ |
| Android Chrome / Samsung Internet | – | ✓ | – | ✓ |
| Android Firefox | – | – | – | ✓ |
| iPhone / iPad Safari | – | – | ✓ (requires iOS Openloop Connect) | ✓ |
| iPhone / iPad Chrome / Firefox / Edge | – | – | – | ✓ |
- ✓ = works / – = not usable (browser API missing, etc.)
- WalletConnect works everywhere as long as you have a compatible wallet (e.g. Openloop Connect) at hand.
- Firefox implements neither WebHID nor WebBluetooth, so device access on Firefox is through WalletConnect.
- Android Chrome exposes a WebHID API in name, but USB-OTG for a hardware wallet is essentially never available on Android — use BLE instead.
- macOS Safari has no WebHID / WebBluetooth support, and there is currently no Openloop Safari extension for macOS. On macOS Safari, only WalletConnect is available.
2.2 Extension version
- Runs on Chrome / Microsoft Edge (Chromium-based). No Firefox or Safari extension version.
- The extension version connects to Openloop over USB (WebHID) and also supports dApp integration (§10).
2.3 Using Openloop Pay on iPhone / iPad Safari
Safari does not implement WebHID or WebBluetooth, so it cannot talk to an Openloop device directly. Install the iOS Openloop Connect app and enable the Safari extension it bundles — this bridges iPhone / iPad Safari to the Openloop device.
Setup:
- Install “Openloop Connect” from the App Store (iPhone / iPad).
- Open Settings → Safari → Extensions.
- Tap Openloop Connect and switch it On.
- Set Permissions → All Websites to Allow (recommended). Or grant only crypto.haudi.jp from the “AA” button next to Safari’s address bar → Website Settings when you first open Openloop Pay.
- Reopen Openloop Pay. The connect screen will now list your Openloop over Bluetooth.
A macOS Safari extension for Openloop Connect is not currently shipped. On macOS, to use Openloop Pay with a hardware wallet via Bluetooth, connect through WalletConnect (QR code) using the Openloop Connect desktop app or an Openloop Connect on your phone (§3.3).
The iOS Openloop Connect app also works as a WalletConnect-compatible wallet (§3.3), independently of the Safari extension. WalletConnect works whether or not the Safari extension is enabled.
2.4 QR code reading
- On both smartphone and desktop, the browser needs camera permission. Some browsers may not support this (see §7).
3. Connecting a wallet
When you open the app, the “Connect a wallet” screen appears. Choose how to connect.
3.1 Connect over USB (desktop)
- Connect Openloop to your desktop with USB.
- Choose Openloop (USB).
- In the browser’s device chooser, select your Openloop (first time only).
- Once connected, that account’s balances appear.
The browser’s USB device chooser may not open inside the extension’s side panel. In that case, connect from a full tab. Once you’ve granted access, it reconnects without the chooser next time.
3.2 Connect over Bluetooth (smartphone)
- Turn on Openloop and enable Bluetooth.
- Start connecting in the app and pick your Openloop from the list.
- After pairing, that account’s balances appear.
3.3 Connect via WalletConnect
- Choose WalletConnect.
- Pick the wallet you want to connect (e.g. Openloop Connect) from the list, or scan the QR code.
- Approve the connection on the wallet’s side.
Right after connecting, the selected wallet may still be on the network it used last. If the network isn’t switched automatically when you send, set the network on the wallet’s side.
4. Checking balances
Once connected, the main screen shows:
- Wallet card — the current account’s address, a badge for the connection method, and copy / disconnect buttons.
- Assets — the balances of the tokens you chose to show. Use the reload button at the top right to fetch the latest balances.
- Gas (fee) assets — the native tokens used to pay transaction fees (gas). These are used only for fees and appear automatically based on the networks you use.
You choose which tokens and networks appear under “Assets” in the next chapter, “Manage tokens & networks.” Gas native tokens appear automatically for the networks your assets are on, so you normally don’t need to select them separately.
4.1 Showing testnets
Turn on Show testnets to add testnet tokens and networks to the list (their gas coins are shown too). This is useful for testing. When it’s off, testnets appear neither in balances nor in the lists. Leave it off for normal use.
5. Manage tokens & networks
This screen is where you choose which tokens — and on which networks — to show and send. Open it from the Manage tokens & networks link on the connect screen, or the manage button (coin icon) on the balances screen.
The screen is divided into sections. The basic rule is: built-in items (shipped with the app) can’t be removed; added items (ones you brought in) can. Alternating sections have a tinted background to keep them visually separate.
- Built-in tokens — JPYC, USDC, USDT. Use the per-network checkboxes to choose which currency × network combinations to show and send.
- Native tokens (select when sending) — each network’s gas coin (ETH, POL, AVAX, KAIA, …). Check these only when you want to send them. Even unchecked, if you hold them they appear automatically under “Gas (fee) assets.”
- Added tokens — tokens you’ve added. Remove each with its trash icon. Add new ones from Add a token.
- Built-in networks / Added networks — the networks in use. Built-in ones can’t be removed; added ones can (removing a network also removes the tokens on it).
Each screen has a breadcrumb at the top (e.g. Home › Manage tokens & networks › Add a token) so you can see where you are. Tap any crumb to jump straight to that screen. Back goes up one level.
5.1 Adding a token
- Press Add a token.
- Search by symbol or name.
- Pick a result to see the networks that token is available on.
- Check the networks you want to add it on (you can pick several). It’s added the moment you check it.
Networks this app has no RPC endpoint for can’t read balances or broadcast, so they aren’t listed. For a token or network that isn’t listed, use “Not found? Add manually” to enter a contract address or RPC by hand (at your own risk — shown as “unverified”).
5.2 Confirming a deletion
Deleting a token or network shows a confirmation. Deleting a network makes clear that the tokens on that network are removed too.
5.3 Export / import settings
Buttons at the bottom let you export / import your token and network settings (as a JSON file) — handy for moving your setup to another device. Importing shows a confirmation that it will overwrite your current settings, along with an integrity check.
6. Sending
6.1 Steps to send
- In the send panel, choose the token (currency × network) you want to send.
- Enter the recipient (type an address, or pick one from the address book).
- Enter the amount.
- Press Send.
- A confirmation screen appears. Check the recipient (shown in full), the amount, and the network.
- Press Approve and sign with the connected wallet (e.g. the Openloop device).
- When the send completes, the transaction ID and a link to the block explorer are shown.
6.2 About the confirmation screen
- The recipient is shown in full — never abbreviated. Always check it.
- A caution is shown when sending on mainnet.
- The confirmation screen shows an “Auto-closes in N seconds” countdown. If left untouched, it closes automatically for safety (nothing is sent). Pressing Approve stops the countdown.
- You can close the confirmation with Cancel. Cancel stays usable during a WalletConnect send in case the wallet is slow to respond.
6.3 Address book
You can save a recipient with a label of your choice. Next time, just pick it from the address book to fill in the recipient.
7. Loading a payment from a QR code
When you read a payment-request QR code, the send panel’s fields (token, recipient, amount) are filled in automatically. There are two ways to read it.
7.1 Read with the in-app scanner
- Press the QR button at the top right of the send panel.
- The camera starts; point it at the QR code (it reads automatically).
- If the camera isn’t available, you can paste the code instead.
7.2 Read with the stock camera (printed QR)
A printed payment link posted by a store can be read with your phone’s stock camera. It shows a link; tapping it opens Openloop Pay with the payment pre-filled.
7.3 What happens after reading
- If everything needed (token, recipient, amount) is present, the confirmation screen opens directly. It shows “Loaded from a scanned code,” and you can review and approve.
- If something is missing, you’re told what was loaded and prompted to enter the missing fields.
A standard format (EIP-681) is used so printed paper QRs work. Split QR formats like BBQr are not used.
8. Switching accounts
A single Openloop has multiple accounts. Use Switch account on the wallet card to change which account is shown and used for sending.
- The account you pick is remembered on this screen and shown automatically next time.
- Press Switch account only when you want to use a different one.
9. History and CSV export
Your send records appear in the History on the main screen.
- From each transaction ID, you can view details in a block explorer.
- Use the export button at the top right of the history to export your records as a CSV file — handy for accounting and bookkeeping.
History is stored only on your device (browser). It is never sent to any external server.
10. dApp integration (extension only)
The browser-extension build of Openloop Pay can connect directly to dApps (decentralized apps) on the web. Connection and signature requests from a dApp are relayed through Openloop Pay to your Openloop device, where you always review and approve the final action on-device.
The web app and the smartphone build do not integrate with dApps. To connect to dApps, install the Openloop Pay extension in your desktop browser.
10.1 How dApp connections work
- The extension exposes an EIP-1193 provider and announces itself via EIP-6963. dApps see it in their wallet picker as “Openloop Pay”.
- Access is granted per tab. Each tab where you open a dApp is allowed and managed independently; opening the same site in another tab creates a separate connection.
- Every send or signature request is shown in Openloop Pay and must also be reviewed and approved on the Openloop device screen.
10.2 See which sites are connected
You can check the list of sites currently allowed to see your wallet at any time.
- Tap ⓘ to open the Info screen.
- Choose Settings ›.
- Choose dApp connections ›.
- Every connection is listed, each showing the tab number and connect time, plus the site’s host name.
Connections are per browser tab. Opening and connecting the same site in more than one tab creates a separate connection on its own row (in the example above,
app.uniswap.orgappears twice — as “Tab 1” and “Tab 3”). Closing a tab automatically ends that tab’s connection, and disconnecting is done per tab.
10.3 Disconnect one tab, or disconnect all
- Press the Disconnect button on a row to revoke just that connection (that tab). It can no longer see your address; it must request access again next time. Other tabs and other sites stay connected.
- Press Disconnect all at the bottom to revoke every site (every tab) at once. This also disconnects Openloop Pay from the Openloop device.
- The Disconnect button on the wallet card does the same thing — disconnecting the device also disconnects every dApp (no site can see an address that is no longer loaded).
10.4 When the side panel is closed
If a dApp requests an action (signing, switching accounts, …) while the Openloop Pay side panel is closed, a small hint popup appears. Press Open to open the side panel, then retry the action in the dApp.
11. Security
Openloop Pay is built to help you send safely.
- A companion wallet with no keys of its own — Openloop Pay stores no private key or seed phrase and holds no wallet itself. Your keys live only inside the Openloop device (or your wallet). Unlike wallets that keep an (encrypted) key in the browser, even if the web app or extension were compromised, there are no secrets inside to steal.
- Non-custodial — private keys stay inside the Openloop device (or your wallet). Openloop Pay never stores or accesses them.
- Review before signing — you always review the details (recipient, amount, network) on the confirmation screen before approving. When signing with Openloop, you can also check the details on the device screen.
- Connected-device verification — before signing, it checks that the connected device matches the account on screen. If a different device is connected, it shows an error and prevents sending from the wrong account.
- Confirmation auto-close — if you leave the confirmation screen open, it closes automatically for safety.
- Full recipient address — the recipient address is always shown in full, never abbreviated.
- Per-tab dApp access (extension only) — dApp connections are granted per tab. Opening the same site in another tab creates a separate, independent connection. You can disconnect any connection — or all of them at once — from Info → Settings → dApp connections (§10).
11.1 Precautions
- Crypto transactions cannot be undone. Always check the recipient and amount.
- Never share your recovery phrase. Openloop Pay will never ask for it.
- Always check the contents of a scanned QR code or payment request before sending.
12. Troubleshooting
- The camera isn’t available / permission is denied
- Allow camera use in your browser settings. You may be able to allow it from the camera icon in the address bar. Some browsers (such as an extension side panel) can’t use the camera; in that case, paste the code instead.
- The USB Openloop doesn’t appear in the chooser (extension)
- The USB chooser may not open in the extension side panel. Try connecting from a full tab. Also, if Openloop Connect or similar is using the same device, USB may be occupied and unavailable.
- A network I want to add isn’t listed
- Networks this app has no RPC endpoint for can’t read balances or broadcast, so they aren’t listed. If you know the RPC, add it by hand from “Not found? Add manually.”
- WalletConnect shows “cannot connect”
- The connection may be taking time to establish. Wait a moment and try again.
- The send confirmation won’t close / there’s no response
- It’s waiting for a response from the connected wallet. Close it with Cancel and try again.
- The network doesn’t match
- The WalletConnect wallet may be on a different network than the one you want to send on. Set the network on the wallet’s side.
13. Specifications
13.1 Supported tokens (built-in)
Openloop Pay supports EVM only — Ethereum and EVM-compatible chains. The following three stablecoins ship built in and are ready to send and receive without any setup.
| Token | Supported mainnets |
|---|---|
| JPYC | Ethereum / Polygon / Avalanche C-Chain / Kaia (4 chains) |
| USDC | Ethereum / Polygon / Avalanche C-Chain / Base / Arbitrum One / OP Mainnet (6 chains, Circle-issued native USDC) |
| USDT | Ethereum / Polygon (2 chains) |
Testnet JPYC ships on Sepolia / Polygon Amoy / Avalanche Fuji / Kaia Kairos (4 chains — enable Show testnets, §4.1).
13.2 Supported networks (built-in)
| Type | Networks |
|---|---|
| Mainnets (7) | Ethereum / Polygon / Avalanche C-Chain / Base / Arbitrum One / OP Mainnet / Kaia |
| Testnets (3) | Sepolia / Polygon Amoy / Base Sepolia |
Each network ships with a public RPC endpoint (publicnode family) and a block-explorer URL.
13.3 Added tokens and networks
- Search dictionary — the same token dictionary as the Openloop device (923 symbols / 2,552 contracts), searchable by symbol or name (built-in JPYC / USDC / USDT excluded).
- Manual add (token) — tokens not in the dictionary can be added by contract address + network (shown as “unverified”).
- Add a network — any EVM chain outside the built-in ten can be added by name, RPC URL and explorer URL.
13.4 dApp integration (extension only)
The browser-extension build talks to dApps over the following standards.
| Item | Supported |
|---|---|
| Provider API | EIP-1193 (the window.ethereum
interface) |
| Provider discovery | EIP-6963 (Multi Injected Provider Discovery — coexists with other wallets) |
| Chain ID | EIP-155 / CAIP-2 |
| RPC methods | eth_requestAccounts / eth_accounts /
eth_chainId / eth_sendTransaction
(EIP-1559 type-2 tx) / personal_sign /
eth_signTypedData_v3 / eth_signTypedData_v4
(EIP-712) / wallet_switchEthereumChain
(EIP-3326) / wallet_addEthereumChain
(EIP-3085) |
| Not supported | eth_signTypedData_v1 (legacy — dropped, no type info) /
eth_sign (blind-signing of an opaque hash — a strong red
warning is shown if requested) |
| Access grants | Granted and revoked per tab (the tab where a dApp is open) (§10) |
13.5 WalletConnect
- WalletConnect v2 — supported as the wallet-connection client (Openloop Pay itself is the companion / dApp side, not the wallet).
- Connect by scanning a QR code or picking from the wallet list (Openloop Connect and any WalletConnect v2-compatible wallet).
- Sends are broadcast on the connected wallet’s current network. To send on a different network, switch it on the wallet’s side.
13.6 Payment-request QR
- EIP-681 — the standard
ethereum:URI format (contract address /transferfunction / chain ID / amount). Printed paper QRs can be opened from your phone’s stock camera (§7). - Split-QR formats such as BBQr are not used.
13.7 Web app vs. browser extension
| Item | Web app | Browser extension (Chrome / Edge) |
|---|---|---|
| Runs on | Desktop and smartphone | Desktop only |
| Openloop (USB) | Yes (WebHID-capable browser) | Yes (may need full-tab consent) |
| Openloop (Bluetooth) | Yes (supported smartphones) | No (blocked by extension permissions) |
| WalletConnect | Yes | Yes |
| dApp integration (EIP-6963 / EIP-1193) | No | Yes |
| Camera QR scan | Yes | Limited (may not work in the side panel) |
| Open from payment link | Yes | Yes |
| Storage for history / address book | In the browser | In the extension storage |
14. Contact
If you have any questions or trouble, please contact us.
Haudi Crypto, Inc. Email: support@crypto.haudi.jp
You can also open the version, links to each document, and the settings screen (payment sound, dApp connections) from the in-app info (ⓘ) button.
Related documents: Terms of Service / Privacy Policy / Licenses