UCAN Devtools

UCAN Devtools is a browser extension that adds a DevTools panel for inspecting and debugging UCANs found in browser traffic (for example UCANs carried in request headers).

It supports UCAN 1.0 (DAG-CBOR envelopes) including both UCAN delegations and invocations.

Relevant specs

• UCAN core spec
• Delegation payload
• Invocation payload
• UCAN HTTP Bearer Token

Installation

Pre-built extension packages are available in GitHub Releases.

Download the appropriate zip for your browser:

• *-chrome.zip for Chrome/Edge/Brave
• *-firefox.zip for Firefox
• Source archives are auto-generated by GitHub; you don’t need them to install the extension.

Install from release zip (recommended)

Chrome / Edge / Brave

1. Download the *-chrome.zip from the releases page and unzip it.
2. Visit chrome://extensions, enable Developer mode, and click Load unpacked.
3. Select the unzipped folder.

Firefox

1. Download the *-firefox.zip from the releases page and unzip it.
2. Visit about:debugging#/runtime/this-firefox and click Load Temporary Add-on….
3. Select manifest.json inside the unzipped folder.

If the panel doesn’t appear, ensure the extension is enabled and reopen DevTools (Ctrl+Shift+I / Cmd+Opt+I).

Getting started (for contributors)

Prerequisites

• Node.js
• pnpm

Install deps

• pnpm install

Build

• Chrome (MV3): pnpm build
  • Output: .output/chrome-mv3
• Firefox (MV2): pnpm build:firefox
  • Output: .output/firefox-mv2

Install locally

Chrome

1. Run pnpm build
2. Open chrome://extensions
3. Enable Developer mode
4. Click Load unpacked and select .output/chrome-mv3

Firefox

1. Run pnpm build:firefox
2. Open about:debugging#/runtime/this-firefox
3. Click Load Temporary Add-on…
4. Select .output/firefox-mv2/manifest.json

Dev (optional)

• Chrome: pnpm dev
• Firefox: pnpm dev:firefox

Package (optional)

• Chrome zip: pnpm zip
• Firefox zip: pnpm zip:firefox

License

MIT © 2025 Chris Waring