- Category
- Developer Tools
- Rank
- No. 2964Tools index
Previous survey · No. 2821 ·
- Pricing
- Open Source
- Type
- TOOL
- Use case
- Coding
- Interfaces
- SDK
- Builder
- browserbase
- GitHub
- 9 stars
- Date
About
Extend the Chrome Debug Protocol with custom commands, events, and middlewares. Modify browser behavior and change how stagehand, playwright, and puppeteer drivers work.
What it does
ModCDP places a browser extension service worker behind an ordinary Chrome debugging connection. That worker can execute expressions with extension APIs available, while a client or proxy routes browser messages through it. Existing automation clients keep speaking the familiar protocol.
Why it's ranked here
This is compelling infrastructure for teams blocked by gaps in Chrome’s debugging interface. It preserves compatibility with existing automation clients while moving browser-specific logic into an extension service worker. Multiple routing and transport choices make it unusually flexible, though that flexibility brings setup cost.
What's good
Custom behavior remains accessible through standard debugging sessions, including those managed by Playwright and Puppeteer. Schemas validate custom command inputs and results. TypeScript, Python, and Go expose aligned public surfaces, while demos exercise real browser traffic, middleware, events, and latency reporting.
Tradeoffs
The architecture requires a browser extension plus careful launcher, injector, router, server, and transport configuration. Node users need version 22 or newer. Native messaging depends on Chrome launching a configured host. Reverse mode supports one local browser and one extension connection per proxy process.
How to use it well
Choose it when browser automation needs extension APIs, richer browser events, or protocol-level interception without replacing an established driver. Start with the loopback demo, then narrow routing as requirements become clear. It is not a general automation framework, nor does it independently provide stable page and element references.
Technical notes+
extension/src/service_worker.ts starts ModCDPServer inside the MV3 service worker. js/src/index.ts, python/modcdp/__init__.py, and go/modcdp/modcdp.go expose deliberately synchronized client, launcher, injector, router, transport, translation, and type surfaces. package.json publishes an ESM npm package, requires Node >=22, declares Zod as its runtime dependency, and exposes the proxy CLI as a module entry. js/scripts/build-extension-assets.mjs bundles for Chrome 116, creates a reproducible extension archive, and copies that archive into the Python and Go packages. vitest.config.ts discovers tests under js/test.
Observed
- Primary language surface
- TypeScript implements the Node client, server, proxy, extension, and build tooling.
- Additional language interfaces
- Python and Go packages mirror the public client, launcher, injector, transport, router, translation, and type surfaces.
- Packaging
- Published as an ESM npm package, with bundled extension archives also copied into Python and Go packages.
- Interfaces
- Provides language libraries and a transparent command-line CDP proxy.
- Browser platform
- Targets Chromium through an MV3 extension service worker and standard CDP connections.
- Operating system demos
- Repository demos launch Chrome headful on macOS and in new headless mode on Linux.
- Tests
- The repository contains JavaScript and Go test files, with Vitest configured for the JavaScript test tree.
Read from README.md, package.json, vitest.config.ts, js/src/index.ts, go/modcdp/modcdp.go, go/modcdp/modcdp_test.go, python/modcdp/__init__.py, extension/src/service_worker.ts, js/scripts/build-extension-assets.mjs, js/src/proxy/cli.ts, go/modcdp/client/CDPTypes.go, extension/src/pages/options.ts, python/modcdp/types/__init__.py, python/modcdp/client/__init__.py, python/modcdp/router/__init__.py.
What it can do
Add custom commands to Chrome Debug Protocol
Custom command definitions → Extended CDP with new commands
Add custom events to Chrome Debug Protocol
Custom event definitions → Extended CDP with new events
Install middleware for Chrome Debug Protocol
Middleware functions → Modified CDP request/response pipeline
Modify browser behavior through CDP extensions
Browser behavior modification rules → Altered browser runtime behavior
Change Playwright driver behavior
Playwright driver modifications → Modified Playwright automation behavior
Change Puppeteer driver behavior
Puppeteer driver modifications → Modified Puppeteer automation behavior
Change Stagehand driver behavior
Stagehand driver modifications → Modified Stagehand automation behavior
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Editorially curated, with community endorsements as a secondary signal. Corrections welcome.