Workers Devtools

This package contains a Workers specific version of Chrome Devtools that is used by the Wrangler dev command and other applications. It is a customized fork of Chrome DevTools specifically tailored for debugging Cloudflare Workers. This package provides Worker-specific functionality through carefully maintained patches on top of Chrome DevTools.

Overview

This package is used across multiple Cloudflare products:

• Workers Playground (workers-playground)
• Quick Editor (@cloudflare/quick-edit)
• Wrangler CLI via the InspectorProxy

Features

Our customized DevTools implementation provides:

• Source code viewing and live updates
• Network request inspection
• Worker-specific UI optimizations

Development

We maintain this fork by applying patches on top of Chrome DevTools. These patches need to be periodically rebased as Chrome DevTools evolves.

Key Development Tasks:

• Generating patches from our customizations
• Rebasing patches onto new Chrome DevTools versions
• Testing functionality across all integration points

Updating DevTools

We perform quarterly updates to stay current with upstream Chrome DevTools. The update process involves:

1. Cloning the devtools-frontend repo
2. Applying our existing patches
3. Rebasing onto the latest Chrome DevTools
4. Regenerating patches
5. Thorough testing across all integration points

For detailed instructions on updating DevTools, please refer to our internal documentation on keeping devtools up-to-date.

Testing

Two methods are available for testing updates:

Local Development:

• Build and serve DevTools locally
• Test against local Playground instance
• Make targeted fixes as needed

Preview Builds:

On any pull request to the repo on GitHub, you can add the preview:chrome-devtools-patches label to trigger a preview build of the DevTools frontend. This is useful because it will allow you to manually test your changes in a live environment, and with one-click.

Once the preview is built, you will see a comment on the PR with a link to the live URL.

Acceptance Criteria

Our DevTools implementation must maintain full functionality across:

• Console operations (logging, errors, filters)
• Source code viewing and debugging
• Network request inspection
• Worker-specific UI customizations

Contributing

When making changes:

• Keep patches minimal and targeted
• Prefer CSS-based UI modifications
• Test thoroughly across all integration points
• Document any new patches or modifications

Deployment

This package is deployed as a Cloudflare Workers + Assets project. The static DevTools frontend is served directly from Workers Assets, configured via wrangler.jsonc.

Deployments are managed by GitHub Actions:

• deploy-previews.yml:
  • Runs on any PR that has the preview:chrome-devtools-patches label.
  • Uploads a preview version (without activating it in production) via wrangler versions upload.
  • The preview URL is posted as a comment on the PR.
• changesets.yml:
  • Runs when a "Version Packages" PR, containing a changeset that touches this package, is merged to main.
  • Deploys this package to production via wrangler deploy.
  • Production is accessible via the custom domain [https://devtools.devprod.cloudflare.dev/].

Source: packages/chrome-devtools-patches/README.md