unclecode/crawl4ai · error · NotImplementedError

Browser type {self.browser_type} not supported

Error message

Browser type {self.browser_type} not supported

What it means

The managed browser launcher builds a subprocess command line per browser type and only knows how to do so for 'chromium' and 'firefox'. Any other browser_type string falls through to NotImplementedError, naming the unsupported value.

Source

Thrown at crawl4ai/browser_manager.py:406:7237

        if self.browser_type == "chromium":
            args = [
                f"--remote-debugging-port={self.debugging_port}",
                f"--user-data-dir={self.user_data_dir}",
            ]
            if self.headless:
                args.append("--headless=new")
        elif self.browser_type == "firefox":
            args = [
                "--remote-debugging-port",
                str(self.debugging_port),
                "--profile",
                self.user_data_dir,
            ]
            if self.headless:
                args.append("--headless")
        else:
            raise NotImplementedError(f"Browser type {self.browser_type} not supported")

        return base_args + args

    async def cleanup(self):
        """Cleanup browser process and temporary directory"""
        # Set shutting_down flag BEFORE any termination actions
        self.shutting_down = True

        if self.browser_process:
            try:
                # For builtin browsers that should persist, we should check if it's a detached process
                # Only terminate if we have proper control over the process
                if not self.browser_process.poll():
                    # Process is still running
                    self.browser_process.terminate()
                    # Wait for process to end gracefully
                    for _ in range(10):  # 10 attempts, 100ms each
                        if self.browser_process.poll() is not None:

View on GitHub (pinned to 7e80152142)

Solutions

1. Use browser_type='chromium' or browser_type='firefox' exactly (lowercase)
2. If you named a concrete binary ('chrome', 'edge'), switch to 'chromium' and point the binary/path option at your executable if the config supports it
3. For other engines, use Playwright-based crawling instead of the managed native launcher

Example fix

# before
BrowserConfig(browser_type="chrome")
# after
BrowserConfig(browser_type="chromium")

SUPPORTED_BROWSERS = {"chromium", "firefox"}

def validate_browser_type(browser_type: str) -> str:
    if browser_type not in SUPPORTED_BROWSERS:
        raise ValueError(
            f"unsupported browser_type {browser_type!r}; use one of {sorted(SUPPORTED_BROWSERS)}"
        )
    return browser_type

def is_supported_browser(browser_type) -> bool:
    return isinstance(browser_type, str) and browser_type in {"chromium", "firefox"}

try:
    args = browser._build_args()  # or start()
except NotImplementedError:
    # reconfigure and retry with a supported engine
    browser.browser_type = "chromium"
    args = browser._build_args()

When it happens

Trigger: Setting browser_type to anything other than 'chromium' or 'firefox' in the managed/native browser config — e.g. 'chrome', 'google-chrome', 'webkit', 'edge', 'safari', or a typo like 'Chromium' (case-sensitive).

Common situations: Users writing browser_type='chrome' because that is the Playwright/Puppeteer spelling; attempting WebKit/Edge support that the launcher does not implement; case mismatches after a config refactor.

Related errors

• Hook '{hook_name}' must be a callable function, got {type(ho
• URL must have a valid hostname
• too many webhook headers
• invalid webhook header name: {name!r}
• webhook header not allowed: {name}

AI-assisted analysis of unclecode/crawl4ai@7e80152142 (2026-08-14). Data as JSON: /api/errors/d0fe6fb0ca702336. Report an issue: GitHub.