Prefix-Based Input Handling in Crawl4AI

This guide will walk you through using the Crawl4AI library to crawl web pages, local HTML files, and raw HTML strings. We'll demonstrate these capabilities using a Wikipedia page as an example.

Crawling a Web URL

To crawl a live web page, provide the URL starting with http:// or https://, using a CrawlerRunConfig object:

import asyncio
from crawl4ai import AsyncWebCrawler, CacheMode, CrawlerRunConfig

async def crawl_web():
    config = CrawlerRunConfig(cache_mode=CacheMode.BYPASS)
    async with AsyncWebCrawler() as crawler:
        result = await crawler.arun(
            url="https://en.wikipedia.org/wiki/apple", 
            config=config
        )
        if result.success:
            print("Markdown Content:")
            print(result.markdown)
        else:
            print(f"Failed to crawl: {result.error_message}")

asyncio.run(crawl_web())

Crawling a Local HTML File

To crawl a local HTML file, prefix the file path with file://.

import asyncio
from crawl4ai import AsyncWebCrawler, CacheMode, CrawlerRunConfig

async def crawl_local_file():
    local_file_path = "/path/to/apple.html"  # Replace with your file path
    file_url = f"file://{local_file_path}"
    config = CrawlerRunConfig(cache_mode=CacheMode.BYPASS)

    async with AsyncWebCrawler() as crawler:
        result = await crawler.arun(url=file_url, config=config)
        if result.success:
            print("Markdown Content from Local File:")
            print(result.markdown)
        else:
            print(f"Failed to crawl local file: {result.error_message}")

asyncio.run(crawl_local_file())

Crawling Raw HTML Content

To crawl raw HTML content, prefix the HTML string with raw:.

import asyncio
from crawl4ai import AsyncWebCrawler, CacheMode
from crawl4ai.async_configs import CrawlerRunConfig

async def crawl_raw_html():
    raw_html = "<html><body><h1>Hello, World!</h1></body></html>"
    raw_html_url = f"raw:{raw_html}"
    config = CrawlerRunConfig(cache_mode=CacheMode.BYPASS)

    async with AsyncWebCrawler() as crawler:
        result = await crawler.arun(url=raw_html_url, config=config)
        if result.success:
            print("Markdown Content from Raw HTML:")
            print(result.markdown)
        else:
            print(f"Failed to crawl raw HTML: {result.error_message}")

asyncio.run(crawl_raw_html())

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Complete Example

Below is a comprehensive script that:

1. Crawls the Wikipedia page for "Apple."
2. Saves the HTML content to a local file (apple.html).
3. Crawls the local HTML file and verifies the markdown length matches the original crawl.
4. Crawls the raw HTML content from the saved file and verifies consistency.

import os
import sys
import asyncio
from pathlib import Path
from crawl4ai import AsyncWebCrawler, CacheMode, CrawlerRunConfig

async def main():
    wikipedia_url = "https://en.wikipedia.org/wiki/apple"
    script_dir = Path(__file__).parent
    html_file_path = script_dir / "apple.html"

    async with AsyncWebCrawler() as crawler:
        # Step 1: Crawl the Web URL
        print("\n=== Step 1: Crawling the Wikipedia URL ===")
        web_config = CrawlerRunConfig(cache_mode=CacheMode.BYPASS)
        result = await crawler.arun(url=wikipedia_url, config=web_config)

        if not result.success:
            print(f"Failed to crawl {wikipedia_url}: {result.error_message}")
            return

        with open(html_file_path, 'w', encoding='utf-8') as f:
            f.write(result.html)
        web_crawl_length = len(result.markdown)
        print(f"Length of markdown from web crawl: {web_crawl_length}\n")

        # Step 2: Crawl from the Local HTML File
        print("=== Step 2: Crawling from the Local HTML File ===")
        file_url = f"file://{html_file_path.resolve()}"
        file_config = CrawlerRunConfig(cache_mode=CacheMode.BYPASS)
        local_result = await crawler.arun(url=file_url, config=file_config)

        if not local_result.success:
            print(f"Failed to crawl local file {file_url}: {local_result.error_message}")
            return

        local_crawl_length = len(local_result.markdown)
        assert web_crawl_length == local_crawl_length, "Markdown length mismatch"
        print("✅ Markdown length matches between web and local file crawl.\n")

        # Step 3: Crawl Using Raw HTML Content
        print("=== Step 3: Crawling Using Raw HTML Content ===")
        with open(html_file_path, 'r', encoding='utf-8') as f:
            raw_html_content = f.read()
        raw_html_url = f"raw:{raw_html_content}"
        raw_config = CrawlerRunConfig(cache_mode=CacheMode.BYPASS)
        raw_result = await crawler.arun(url=raw_html_url, config=raw_config)

        if not raw_result.success:
            print(f"Failed to crawl raw HTML content: {raw_result.error_message}")
            return

        raw_crawl_length = len(raw_result.markdown)
        assert web_crawl_length == raw_crawl_length, "Markdown length mismatch"
        print("✅ Markdown length matches between web and raw HTML crawl.\n")

        print("All tests passed successfully!")
    if html_file_path.exists():
        os.remove(html_file_path)

if __name__ == "__main__":
    asyncio.run(main())

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Conclusion

With the unified url parameter and prefix-based handling in Crawl4AI, you can seamlessly handle web URLs, local HTML files, and raw HTML content. Use CrawlerRunConfig for flexible and consistent configuration in all scenarios.