unclecode/crawl4ai · error · ValueError

Process HTML, Failed to extract content from the website: {u

Error message

Process HTML, Failed to extract content from the website: {url}, error: {str(e)}

What it means

Catch-all ValueError from AsyncWebCrawler.process_html: any non-InvalidCSSSelectorError exception raised inside the scraping/processing pipeline is wrapped with the URL and the original error text. The underlying str(e) identifies the true fault; the wrapper only adds context.

Source

Thrown at crawl4ai/async_webcrawler.py:794:1852

            # add keys from kwargs to params that doesn't exist in params
            params.update({k: v for k, v in kwargs.items()
                          if k not in params.keys()})

            ################################
            # Scraping Strategy Execution  #
            ################################
            result: ScrapingResult = scraping_strategy.scrap(
                url, html, **params)

            if result is None:
                raise ValueError(
                    f"Process HTML, Failed to extract content from the website: {url}"
                )

        except InvalidCSSSelectorError as e:
            raise ValueError(str(e))
        except Exception as e:
            raise ValueError(
                f"Process HTML, Failed to extract content from the website: {url}, error: {str(e)}"
            )

        # Extract results - handle both dict and ScrapingResult
        if isinstance(result, dict):
            cleaned_html = sanitize_input_encode(
                result.get("cleaned_html", ""))
            media = result.get("media", {})
            links = result.get("links", {})
            metadata = result.get("metadata", {})
        else:
            cleaned_html = sanitize_input_encode(result.cleaned_html)
            media = result.media.model_dump()
            links = result.links.model_dump()
            metadata = result.metadata

        ################################
        # Generate Markdown            #

View on GitHub (pinned to 7e80152142)

Solutions

Read the ', error:' suffix - it names the real exception; fix that first
For parse errors on pre-fetched html, sanitize first: html = html.encode('utf-8', 'ignore').decode() and cap size
If the error text points into your custom strategy/generator, unit-test it directly against the failing page's saved HTML
Persist the failing html (curl the URL) so you can reproduce outside the crawler

Example fix

# before
result = await crawler.arun(url=url, config=config)  # ValueError: ..., error: ExpatError

# after
try:
    result = await crawler.arun(url=url, config=config)
except ValueError as e:
    logger.error("extract failed for %s: %s", url, e)
    save_debug(url)  # keep the page for offline repro
    result = None

Defensive patterns

Strategy: try-catch

Validate before calling

# bound and clean pre-fetched HTML before arun(html=...)
html = html[:10_000_000]  # cap size
html = html.encode("utf-8", "ignore").decode("utf-8") if isinstance(html, str) else html

Type guard

def is_processable_html_payload(h) -> bool:
    return isinstance(h, str) and 0 < len(h) <= 10_000_000 and '<' in h

Try / catch

try:
    result = await crawler.arun(url=url, config=config)
except ValueError as e:
    inner = str(e).split(", error: ")[-1]  # unwrap the real cause
    logger.error("process_html failed for %s: %s", url, inner)
    result = None  # or route to a fallback parser

Prevention

Save the failing page's HTML on first failure to enable offline repro
Unit-test custom strategies/generators against real page fixtures
Cap page size at fetch time to avoid parser blowups on huge documents

When it happens

Trigger: Exceptions thrown while parsing html in scrap(): BeautifulSoup/lxml parse errors, memory issues on gigantic pages, KeyError/TypeError bugs in custom strategies or generators, or failures in markdown generation / media extraction steps.

Common situations: Malformed or non-UTF8 html passed via arun(html=...); pages over ~50MB choking the parser; a custom markdown_generator or content_filter raising on unexpected DOM shapes; a library version mismatch (lxml/bs4) inside the scraping path.

Related errors

AI-assisted analysis of unclecode/crawl4ai@7e80152142 (2026-08-14). Data as JSON: /api/errors/5c2a7982b1607a47. Report an issue: GitHub.