BSV 402 Payments by Deggen

BSV 402 Payments automatically handles websites that charge for content using Bitcoin SV (BSV) micropayments. When you visit a page that requires payment, the extension detects the HTTP 402 "Payment Required" response, constructs a BSV blockchain transaction on your behalf using your locally-running BSV wallet, and retries the request with the payment attached — all without any manual steps from you.

Try it out by using this demo website: https://now.bsvblockchain.tech

Prerequisite: You'll need a BRC-100 Wallet like https://desktop.bsvb.tech

This is an implementation of the BRC-0121 protocol, an open standard for machine-to-machine micropayments over HTTP. There are no accounts, no subscriptions, and no intermediaries. The extension talks directly to a BSV wallet running on your own machine (such as the BSV Wallet Daemon), signs a payment transaction locally, and sends it to the site you're visiting. Nothing leaves your browser except the payment transaction itself, and only when you navigate to a page that explicitly requests one.

What data is handled

The only data this extension processes is the BSV payment transaction — a cryptographic record of a micropayment denominated in satoshis (fractions of one BSV). This contains a derived public key used for this specific payment and the transaction amount. It contains no name, email address, password, card number, bank account, or any other personally identifying information. The wallet on your machine generates the transaction; the extension's only job is to attach it to the HTTP request.

Why each permission is needed

Access your data for all websites (host_permissions: <all_urls>): The extension needs to observe HTTP responses from any website in order to detect 402 status codes. It cannot know in advance which sites use BRC-0121 payments, so it monitors all responses and acts only when a 402 with the correct BSV payment headers is present. It does not read, modify, or store the content of any page.
Access browser activity during navigation (webRequest, webRequestBlocking): These permissions allow the extension to intercept outgoing HTTP requests and attach payment headers before they leave the browser. webRequestBlocking specifically is required because the extension needs to hold a request open while it constructs the payment transaction asynchronously with your local wallet — this is a Firefox-specific API that Chrome's equivalent (declarativeNetRequest) replaced with a less flexible alternative. Without this, headers cannot be injected in time.
Access browser tabs (tabs): After detecting a 402, the extension triggers a fresh navigation to the same URL so that the payment headers can be injected into a clean request. This is a technical requirement of how Firefox's request pipeline works — the original 402'd request cannot be retried in-place, so a new navigation must be initiated programmatically.