chrome-remote-interface

chrome-remote-interface is a low-level, asynchronous Python client for the Chrome DevTools Protocol (CDP). It is a Python port of the Node.js chrome-remote-interface package.

The library gives you direct access to Chrome and Chromium debugging domains over WebSocket. It intentionally stays close to CDP: it does not add browser automation concepts such as locators, page objects, or selectors.

Features

• Async WebSocket client built for asyncio.
• One generated, typed Python module for every CDP domain.
• Typed commands, parameters, results, events, payloads, aliases, and enums.
• Event listeners with either callbacks or awaitable one-shot waits.
• Flattened CDP sessions through the session_id argument.
• Chrome discovery helpers compatible with the Node.js package.
• Raw client.send(...) access for protocol additions not in the bundled schema.
• Command-line tools for listing targets, creating targets, and inspecting a running browser.

Requirements

• Python 3.10 or newer.
• Chrome or Chromium started with remote debugging enabled.

Install the package from PyPI:

python -m pip install chrome-remote-interface

Start a debugging browser on the default endpoint (localhost:9222):

chrome --remote-debugging-port=9222

For a separate profile, add --user-data-dir so that the command can run next to an existing Chrome instance. See examples/README.md for a complete setup and runnable examples.

Quick start

The package is installed as chrome-remote-interface but imported as cdp:

import asyncio

from cdp import connect


async def main() -> None:
    client = await connect()
    try:
        await client.Page.enable()

        loaded = client.Page.loadEventFired()
        navigation = await client.Page.navigate(url="https://example.com")
        await loaded
        print(f"Loaded frame: {navigation['frameId']}")
    finally:
        await client.close()


asyncio.run(main())

connect() applies its timeout to discovery and the WebSocket handshake. For long-running commands, set command_timeout to bound how long a command may wait for a response. A timed-out command is cancelled and removed from the pending-request table:

client = await connect(command_timeout=10)
try:
    await client.Page.enable()
finally:
    await client.close()

The connection close handshake is bounded by close_timeout (five seconds by default). You can also use the async context manager to guarantee cleanup:

client = await connect()
async with client:
    await client.Page.enable()

Every command can use keyword arguments or a parameter mapping. Generated domain methods return typed dictionaries, so editors can provide completion and report incorrect fields before runtime.

Events and JavaScript

Subscribe to a typed event with a callback and keep the unsubscribe function:

from cdp.domains.network import RequestWillBeSentEvent


def on_request(event: RequestWillBeSentEvent) -> None:
    print(event["request"]["url"])


unsubscribe = client.Network.requestWillBeSent(on_request)
await client.Network.enable()

# Later:
unsubscribe()

Listeners registered with a session_id are removed automatically when Chrome emits Target.detachedFromTarget. They can also be removed explicitly with client.remove_session_listeners(session_id).

CDP values can be optional according to the protocol schema. Narrow them before indexing them:

result = await client.Runtime.evaluate(
    expression="document.title",
    returnByValue=True,
)
remote_object = result["result"]
if "value" in remote_object:
    print(remote_object["value"])

Targets and sessions

The HTTP helpers can list inspectable targets and connect to a specific page:

from cdp import List, connect


targets = await List()
page = next(target for target in targets if target["type"] == "page")
client = await connect(page["id"])

For browser-level connections, attach to a target and pass its session ID to subsequent domain commands:

from cdp import Version, connect


version = await Version()
browser = await connect(version["webSocketDebuggerUrl"])
created = await browser.Target.createTarget(url="about:blank")
attached = await browser.Target.attachToTarget(
    targetId=created["targetId"],
    flatten=True,
)
await browser.Page.enable(session_id=attached["sessionId"])

Discovery helpers

The following async helpers use Chrome's /json endpoints and default to localhost:9222:

Each helper accepts options such as host, port, secure, and timeout. The Node-compatible aliases (Chrome, CDP, list_targets, and so on) are also exported.

Generated CDP domains

Where protocol.json comes from

The source descriptor is chrome-remote-interface/lib/protocol.json. It is the merged Chrome DevTools Protocol schema: Chrome's browser domains plus the JavaScript/runtime domains from the upstream devtools-protocol repository. The copy at cdp/protocol.json is generated automatically for Protocol({"local": True}); do not edit that copy by hand.

Updating the schema

To use the exact protocol supported by a running Chrome, first start Chrome with remote debugging and download its descriptor:

Invoke-WebRequest `
    -Uri http://localhost:9222/json/protocol `
    -OutFile chrome-remote-interface/lib/protocol.json

Or run the repository's Python update script to fetch and merge the latest upstream schema used by the original Node.js project:

python scripts/update_protocol.py

The base URL can be overridden with CDP_PROTOCOL_BASE_URL or the --base-url option.

The script writes the source descriptor and regenerates the Python bindings automatically. If you only replace the source file manually, regenerate from the repository root with:

python tools/generate_domains.py

The generator validates the descriptor, copies it to cdp/protocol.json, and writes one module per domain under cdp/domains/:

from cdp.domains.page import NavigateParameters, NavigateResult
from cdp.domains.runtime import RemoteObject

tools/generate_stubs.py remains available as a compatibility entry point. When a connected browser advertises newer protocol members, use client.send("Domain.command", ...) as a typed-safe raw fallback.

Examples

The examples/ directory contains small, runnable programs:

• basic_navigation.py — Page.enable, Page.navigate, and load events.
• evaluate.py — Runtime.evaluate and optional result values.
• network_events.py — typed Network request events.
• target_sessions.py — Target creation, attachment, and sessions.

Run them from the repository root with:

python -m examples.basic_navigation

Command-line interface

The package also installs a chrome-remote-interface command:

chrome-remote-interface list
chrome-remote-interface new https://example.com
chrome-remote-interface protocol --local
chrome-remote-interface inspect

Development

Install development dependencies and run the full validation suite:

python -m pip install -e ".[dev]"
python tools/generate_domains.py
python -m unittest discover -s tests
ruff format --check .
ruff check .
pyright
python -m build

License

This project is distributed under the MIT License.