{"record":{"id":"348a6f2078a49a41","repo":"unclecode/crawl4ai","slug":"failed-to-start-browser-e","errorCode":null,"errorMessage":"Failed to start browser: {e}","messagePattern":"Failed to start browser: (.+?)","errorType":"exception","errorClass":"Exception","httpStatus":null,"severity":"critical","filePath":"crawl4ai/browser_manager.py","lineNumber":277,"sourceCode":"                    stderr=subprocess.PIPE,\n                    preexec_fn=os.setpgrp  # Start in a new process group\n                )\n                \n            # If verbose is True print args used to run the process\n            if self.logger and self.browser_config.verbose:\n                self.logger.debug(\n                    f\"Starting browser with args: {' '.join(args)}\",\n                    tag=\"BROWSER\"\n                )    \n                \n            # We'll monitor for a short time to make sure it starts properly, but won't keep monitoring\n            await asyncio.sleep(0.5)  # Give browser time to start\n            await self._initial_startup_check()\n            await asyncio.sleep(2)  # Give browser time to start\n            return f\"http://{self.host}:{self.debugging_port}\"\n        except Exception as e:\n            await self.cleanup()\n            raise Exception(f\"Failed to start browser: {e}\")\n\n    async def _initial_startup_check(self):\n        \"\"\"\n        Perform a quick check to make sure the browser started successfully.\n        This only runs once at startup rather than continuously monitoring.\n        \"\"\"\n        if not self.browser_process:\n            return\n            \n        # Check that process started without immediate termination\n        await asyncio.sleep(0.5)\n        if self.browser_process.poll() is not None:\n            # Process already terminated\n            stdout, stderr = b\"\", b\"\"\n            try:\n                stdout, stderr = self.browser_process.communicate(timeout=0.5)\n            except subprocess.TimeoutExpired:\n                pass","sourceCodeStart":259,"sourceCodeEnd":295,"githubUrl":"https://github.com/unclecode/crawl4ai/blob/7e801521428ee12509994d39151006f64055ebe3/crawl4ai/browser_manager.py#L259-L295","documentation":"BrowserManager.start() wraps its whole body in try/except: any failure while spawning the browser subprocess or during the initial startup check (0.5s + 2s grace, _initial_startup_check) triggers cleanup() and re-raises the generic message 'Failed to start browser: {e}' with the underlying error embedded. The original exception type is lost — it becomes a plain Exception.","triggerScenarios":"Browser executable missing or wrong browser_type/browser_path in BrowserConfig; the spawned process exits immediately (bad flags, incompatible Chrome version); port already in use for --remote-debugging-port; sandbox/permission errors in Docker; _initial_startup_check detecting early process death.","commonSituations":"Fresh environments without Chrome/Chromium installed; Docker containers missing shared-memory flags (--shm-size) causing early Chromium crashes; wrong browser_path pointing at a non-existent binary; SELinux/AppArmor denying exec; version drift between Playwright and installed Chrome.","solutions":["Read the ': {e}' suffix — it names the real failure (FileNotFoundError, Address already in use, etc.) and fix that.","Verify the browser binary exists: point BrowserConfig(browser_path='/usr/bin/chromium') explicitly or install Chrome/Chromium.","If the port is taken, change BrowserConfig(headless=True, debugging_port=<free port>) or kill the stale process.","In Docker, add --shm-size=1g or BrowserConfig(extra_args=['--no-sandbox','--disable-dev-shm-usage']) for sandbox/shared-memory crashes.","Enable verbose logging (BrowserConfig(verbose=True)) to see the exact launch args and stderr."],"exampleFix":"# before\nbrowser_config = BrowserConfig(browser_type='chromium')  # binary not found -> Failed to start browser\n\n# after\nbrowser_config = BrowserConfig(\n    browser_type='chromium',\n    headless=True,\n    extra_args=['--no-sandbox', '--disable-dev-shm-usage'],\n)","handlingStrategy":"retry","validationCode":"import shutil\nbinary = shutil.which('chromium') or shutil.which('google-chrome') or shutil.which('chrome')\nif not binary:\n    raise SystemExit('no Chromium/Chrome binary found; install it or set browser_path')","typeGuard":null,"tryCatchPattern":"for attempt in range(3):\n    try:\n        async with AsyncWebCrawler(config=browser_config) as crawler:\n            results = await crawler.arun(url)\n            break\n    except Exception as e:\n        if 'Failed to start browser' in str(e) and attempt < 2:\n            await asyncio.sleep(2)\n            continue\n        raise","preventionTips":["Pre-flight check the browser binary path before starting crawls.","In Docker add --shm-size and --no-sandbox args.","Log the ': {e}' suffix to capture the real launch error.","Keep a free debugging_port per instance."],"tags":["browser-manager","startup","playwright","environment"],"backgroundTag":null,"analyzedSha":"7e801521428ee12509994d39151006f64055ebe3","analyzedAt":"2026-08-14T20:46:20.673Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}