Live demo

Balance watcher

Watch an ETH balance through a hash-pinned worker running in a null-origin sandbox.

Connection

Worker

Bootstrap RPC URL

Worker RPC URL

Specifier contract

Worker config (§7.1)

Arbitrary JSON, defined by the network — leave it blank if the worker takes none.

Watch

Address

idle

Balance

— ETH

Run it as a browser extension

The same demo, packaged for Chrome with @anon-rpc/browser-extension-harness. A service worker owns the harness, an offscreen document holds the null-origin sandbox, and the worker stays verified and running between popup opens.

Download extension (44 KB)

Unzip it — Chrome loads a folder, not an archive.
Open chrome://extensions and turn on Developer mode.
Choose Load unpacked and pick the unzipped folder.
Open the extension's popup and press Start watching.

Unsigned and not in the Chrome Web Store: it is a demo of the standard, not a product. The source is impl/demo-extension.

Under the hood: the bootstrap RPC is used once to read workerHash() and workerResolvers() from the specifier contract; the worker bundle is fetched, its keccak256 verified against the pinned hash, and only then executed — inside a Web Worker in a null-origin sandboxed iframe with no access to this page. Balance queries flow through the worker's fetch. Settings persist in your browser.