[Bug]: Identity based browsing fails

[rollaroll]

crawl4ai version

0.7.4

Expected Behavior

to create a new profile correctly.

Current Behavior

When I run this https://github.com/unclecode/crawl4ai/blob/main/docs/examples/identity_based_browsing.py example, An error message occurred while starting Chromium and the new profile could not be created.

Is this reproducible?

Yes

Inputs Causing the Bug

An error message appears when starting the Chromium browser, irrelevant to the input

Steps to Reproduce

use anaconda create a viroment with python 3.13.5
pip install crawl4ai
python ./identity_based_browsing.py

Code snippets

[https://github.com/unclecode/crawl4ai/blob/main/docs/examples/identity_based_browsing.py](url)

OS

Windows

Python version

3.13.5

Browser

Chrome

Browser version

139.0.7258.5

Error logs & Screenshots (if applicable)

[BROWSER]. ℹ Starting browser with args:
C:\Users\nyapas\AppData\Local\ms-playwright\chromium-1181\chrome-win\chrome.exe --remote-debugging-port=9222
--user-data-dir=C:\Users\nyapas.crawl4ai\profiles\test --disable-gpu --disable-gpu-compositing
--disable-software-rasterizer --no-sandbox --disable-dev-shm-usage --no-first-run --no-default-browser-check
--disable-infobars --window-position=0,0 --ignore-certificate-errors --ignore-certificate-errors-spki-list
--disable-blink-features=AutomationControlled --window-position=400,0 --disable-renderer-backgrounding
--disable-ipc-flooding-protection --force-color-profile=srgb --mute-audio --disable-background-timer-throttling
[ERROR]... × Browser process terminated during startup | Code: 0 | STDOUT: | STDERR:
[PROFILE]. ℹ Error creating profile: BrowserType.connect_over_cdp: Unexpected status 503 when connecting to
http://localhost:9222/json/version/.
This does not look like a DevTools server, try connecting via ws://.
Call log:

• retrieving websocket url from http://localhost:9222

[rollaroll]

I've discovered that this issue might be caused by using a proxy. When I tested it on Ubuntu, I encountered the same error message if the v2ray proxy was enabled. After disabling the proxy, it worked correctly on Ubuntu. However, even after disabling the v2ray proxy on Windows, it still didn't work. I still received an error message in the command line when launching the browser, and I couldn't crawl the web content after logging in:
[ERROR]... × Browser process terminated during startup | Code: 0 | STDOUT: | STDERR:

This might be a problem with my Windows proxy configuration (I'm not sure). Finally, I'd like to know if there's a way to use identity-based crawling while still being compatible with proxies.

[SohamKukreti]

@rollaroll Did you face this issue with proxies only or in the identity_based_browsing example?

Potential Root Cause Analysis

After investigating this CDP connection issue, I've identified a potential root cause. The problem is a race condition in our ManagedBrowser.start() method where we attempt to connect to the CDP endpoint before Chrome has fully initialized it.

The Problem

In crawl4ai/browser_manager.py lines 251-255, we have:

# We'll monitor for a short time to make sure it starts properly, but won't keep monitoring
await asyncio.sleep(0.5)  # Give browser time to start
await self._initial_startup_check()
await asyncio.sleep(2)  # Give browser time to start
return f"http://{self.host}:{self.debugging_port}"

This gives Chrome only 2.5 seconds total to:

1. Start the process
2. Initialize all subsystems
3. Set up the CDP debugging server
4. Make it ready to accept connections

However, the BrowserManager.start() method immediately tries to connect via connect_over_cdp() without verifying the endpoint is actually ready, leading to ECONNREFUSED ::1:9222 errors.

Why This Became More Prominent

This issue likely became more noticeable due to:

• Slower systems/VMs taking longer to initialize Chrome
• Non-headless mode requiring additional graphics initialization
• Profile loading (like in identity-based browsing) adding startup overhead
• Recent Chrome versions potentially having longer startup times

The Fix

What we can try:

1. Increase startup delays to 4 seconds total (1s + 3s)
2. Retry logic with up to 30 attempts (15 seconds total wait time)
3. Proper error handling with detailed logging

The fix ensures we only attempt the CDP connection after confirming the endpoint is responsive, eliminating the race condition.