chore: import upstream snapshot with attribution
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# Getting Started with Crawl4AI
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Welcome to **Crawl4AI**, an open-source LLM-friendly Web Crawler & Scraper. In this tutorial, you’ll:
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1. Run your **first crawl** using minimal configuration.
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2. Generate **Markdown** output (and learn how it’s influenced by content filters).
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3. Experiment with a simple **CSS-based extraction** strategy.
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4. See a glimpse of **LLM-based extraction** (including open-source and closed-source model options).
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5. Crawl a **dynamic** page that loads content via JavaScript.
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---
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## 1. Introduction
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Crawl4AI provides:
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- An asynchronous crawler, **`AsyncWebCrawler`**.
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- Configurable browser and run settings via **`BrowserConfig`** and **`CrawlerRunConfig`**.
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- Automatic HTML-to-Markdown conversion via **`DefaultMarkdownGenerator`** (supports optional filters).
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- Multiple extraction strategies (LLM-based or “traditional” CSS/XPath-based).
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By the end of this guide, you’ll have performed a basic crawl, generated Markdown, tried out two extraction strategies, and crawled a dynamic page that uses “Load More” buttons or JavaScript updates.
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---
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## 2. Your First Crawl
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Here’s a minimal Python script that creates an **`AsyncWebCrawler`**, fetches a webpage, and prints the first 300 characters of its Markdown output:
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```python
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import asyncio
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from crawl4ai import AsyncWebCrawler
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async def main():
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async with AsyncWebCrawler() as crawler:
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result = await crawler.arun("https://example.com")
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print(result.markdown[:300]) # Print first 300 chars
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if __name__ == "__main__":
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asyncio.run(main())
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```
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**What’s happening?**
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- **`AsyncWebCrawler`** launches a headless browser (Chromium by default).
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- It fetches `https://example.com`.
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- Crawl4AI automatically converts the HTML into Markdown.
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You now have a simple, working crawl!
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---
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## 3. Basic Configuration (Light Introduction)
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Crawl4AI’s crawler can be heavily customized using two main classes:
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1. **`BrowserConfig`**: Controls browser behavior (headless or full UI, user agent, JavaScript toggles, etc.).
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2. **`CrawlerRunConfig`**: Controls how each crawl runs (caching, extraction, timeouts, hooking, etc.).
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Below is an example with minimal usage:
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```python
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import asyncio
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from crawl4ai import AsyncWebCrawler, BrowserConfig, CrawlerRunConfig, CacheMode
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async def main():
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browser_conf = BrowserConfig(headless=True) # or False to see the browser
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run_conf = CrawlerRunConfig(
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cache_mode=CacheMode.BYPASS
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)
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async with AsyncWebCrawler(config=browser_conf) as crawler:
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result = await crawler.arun(
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url="https://example.com",
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config=run_conf
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)
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print(result.markdown)
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if __name__ == "__main__":
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asyncio.run(main())
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```
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> IMPORTANT: By default cache mode is set to `CacheMode.BYPASS` to have fresh content. Set `CacheMode.ENABLED` to enable caching.
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We’ll explore more advanced config in later tutorials (like enabling proxies, PDF output, multi-tab sessions, etc.). For now, just note how you pass these objects to manage crawling.
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---
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## 4. Generating Markdown Output
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By default, Crawl4AI automatically generates Markdown from each crawled page. However, the exact output depends on whether you specify a **markdown generator** or **content filter**.
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- **`result.markdown`**:
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The direct HTML-to-Markdown conversion.
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- **`result.markdown.fit_markdown`**:
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The same content after applying any configured **content filter** (e.g., `PruningContentFilter`).
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### Example: Using a Filter with `DefaultMarkdownGenerator`
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```python
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from crawl4ai import AsyncWebCrawler, CrawlerRunConfig, CacheMode
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from crawl4ai.content_filter_strategy import PruningContentFilter
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from crawl4ai.markdown_generation_strategy import DefaultMarkdownGenerator
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md_generator = DefaultMarkdownGenerator(
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content_filter=PruningContentFilter(threshold=0.4, threshold_type="fixed")
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)
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config = CrawlerRunConfig(
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cache_mode=CacheMode.BYPASS,
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markdown_generator=md_generator
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)
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async with AsyncWebCrawler() as crawler:
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result = await crawler.arun("https://news.ycombinator.com", config=config)
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print("Raw Markdown length:", len(result.markdown.raw_markdown))
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print("Fit Markdown length:", len(result.markdown.fit_markdown))
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```
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**Note**: If you do **not** specify a content filter or markdown generator, you’ll typically see only the raw Markdown. `PruningContentFilter` may adds around `50ms` in processing time. We’ll dive deeper into these strategies in a dedicated **Markdown Generation** tutorial.
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---
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## 5. Simple Data Extraction (CSS-based)
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Crawl4AI can also extract structured data (JSON) using CSS or XPath selectors. Below is a minimal CSS-based example:
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> **New!** Crawl4AI now provides a powerful utility to automatically generate extraction schemas using LLM. This is a one-time cost that gives you a reusable schema for fast, LLM-free extractions:
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```python
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from crawl4ai import JsonCssExtractionStrategy
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from crawl4ai import LLMConfig
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# Generate a schema (one-time cost)
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html = "<div class='product'><h2>Gaming Laptop</h2><span class='price'>$999.99</span></div>"
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# Using OpenAI (requires API token)
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schema = JsonCssExtractionStrategy.generate_schema(
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html,
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llm_config = LLMConfig(provider="openai/gpt-4o",api_token="your-openai-token") # Required for OpenAI
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)
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# Or using Ollama (open source, no token needed)
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schema = JsonCssExtractionStrategy.generate_schema(
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html,
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llm_config = LLMConfig(provider="ollama/llama3.3", api_token=None) # Not needed for Ollama
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)
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# Use the schema for fast, repeated extractions
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strategy = JsonCssExtractionStrategy(schema)
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```
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For a complete guide on schema generation and advanced usage, see [No-LLM Extraction Strategies](../extraction/no-llm-strategies.md).
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Here's a basic extraction example:
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```python
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import asyncio
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import json
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from crawl4ai import AsyncWebCrawler, CrawlerRunConfig, CacheMode
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from crawl4ai import JsonCssExtractionStrategy
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async def main():
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schema = {
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"name": "Example Items",
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"baseSelector": "div.item",
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"fields": [
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{"name": "title", "selector": "h2", "type": "text"},
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{"name": "link", "selector": "a", "type": "attribute", "attribute": "href"}
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]
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}
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raw_html = "<div class='item'><h2>Item 1</h2><a href='https://example.com/item1'>Link 1</a></div>"
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async with AsyncWebCrawler() as crawler:
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result = await crawler.arun(
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url="raw://" + raw_html,
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config=CrawlerRunConfig(
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cache_mode=CacheMode.BYPASS,
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extraction_strategy=JsonCssExtractionStrategy(schema)
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)
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)
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# The JSON output is stored in 'extracted_content'
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data = json.loads(result.extracted_content)
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print(data)
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if __name__ == "__main__":
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asyncio.run(main())
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```
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**Why is this helpful?**
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- Great for repetitive page structures (e.g., item listings, articles).
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- No AI usage or costs.
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- The crawler returns a JSON string you can parse or store.
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> Tips: You can pass raw HTML to the crawler instead of a URL. To do so, prefix the HTML with `raw://`.
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---
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## 6. Simple Data Extraction (LLM-based)
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For more complex or irregular pages, a language model can parse text intelligently into a structure you define. Crawl4AI supports **open-source** or **closed-source** providers:
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- **Open-Source Models** (e.g., `ollama/llama3.3`, `no_token`)
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- **OpenAI Models** (e.g., `openai/gpt-4`, requires `api_token`)
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- Or any provider supported by the underlying library
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Below is an example using **open-source** style (no token) and closed-source:
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```python
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import os
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import json
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import asyncio
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from pydantic import BaseModel, Field
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from crawl4ai import AsyncWebCrawler, CrawlerRunConfig, LLMConfig
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from crawl4ai import LLMExtractionStrategy
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class OpenAIModelFee(BaseModel):
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model_name: str = Field(..., description="Name of the OpenAI model.")
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input_fee: str = Field(..., description="Fee for input token for the OpenAI model.")
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output_fee: str = Field(
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..., description="Fee for output token for the OpenAI model."
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)
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async def extract_structured_data_using_llm(
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provider: str, api_token: str = None, extra_headers: Dict[str, str] = None
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):
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print(f"\n--- Extracting Structured Data with {provider} ---")
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if api_token is None and provider != "ollama":
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print(f"API token is required for {provider}. Skipping this example.")
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return
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browser_config = BrowserConfig(headless=True)
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extra_args = {"temperature": 0, "top_p": 0.9, "max_tokens": 2000}
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if extra_headers:
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extra_args["extra_headers"] = extra_headers
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crawler_config = CrawlerRunConfig(
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cache_mode=CacheMode.BYPASS,
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word_count_threshold=1,
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page_timeout=80000,
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extraction_strategy=LLMExtractionStrategy(
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llm_config = LLMConfig(provider=provider,api_token=api_token),
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schema=OpenAIModelFee.model_json_schema(),
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extraction_type="schema",
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instruction="""From the crawled content, extract all mentioned model names along with their fees for input and output tokens.
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Do not miss any models in the entire content.""",
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extra_args=extra_args,
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),
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)
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async with AsyncWebCrawler(config=browser_config) as crawler:
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result = await crawler.arun(
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url="https://openai.com/api/pricing/", config=crawler_config
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)
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print(result.extracted_content)
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if __name__ == "__main__":
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asyncio.run(
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extract_structured_data_using_llm(
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provider="openai/gpt-4o", api_token=os.getenv("OPENAI_API_KEY")
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)
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)
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```
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**What’s happening?**
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- We define a Pydantic schema (`PricingInfo`) describing the fields we want.
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- The LLM extraction strategy uses that schema and your instructions to transform raw text into structured JSON.
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- Depending on the **provider** and **api_token**, you can use local models or a remote API.
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---
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## 7. Adaptive Crawling (New!)
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Crawl4AI now includes intelligent adaptive crawling that automatically determines when sufficient information has been gathered. Here's a quick example:
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```python
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import asyncio
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from crawl4ai import AsyncWebCrawler, AdaptiveCrawler
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async def adaptive_example():
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async with AsyncWebCrawler() as crawler:
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adaptive = AdaptiveCrawler(crawler)
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# Start adaptive crawling
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result = await adaptive.digest(
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start_url="https://docs.python.org/3/",
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query="async context managers"
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)
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# View results
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adaptive.print_stats()
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print(f"Crawled {len(result.crawled_urls)} pages")
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print(f"Achieved {adaptive.confidence:.0%} confidence")
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if __name__ == "__main__":
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asyncio.run(adaptive_example())
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```
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**What's special about adaptive crawling?**
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- **Automatic stopping**: Stops when sufficient information is gathered
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- **Intelligent link selection**: Follows only relevant links
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- **Confidence scoring**: Know how complete your information is
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[Learn more about Adaptive Crawling →](adaptive-crawling.md)
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---
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## 8. Multi-URL Concurrency (Preview)
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If you need to crawl multiple URLs in **parallel**, you can use `arun_many()`. By default, Crawl4AI employs a **MemoryAdaptiveDispatcher**, automatically adjusting concurrency based on system resources. Here’s a quick glimpse:
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```python
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import asyncio
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from crawl4ai import AsyncWebCrawler, CrawlerRunConfig, CacheMode
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async def quick_parallel_example():
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urls = [
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"https://example.com/page1",
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"https://example.com/page2",
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"https://example.com/page3"
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]
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run_conf = CrawlerRunConfig(
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cache_mode=CacheMode.BYPASS,
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stream=True # Enable streaming mode
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)
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async with AsyncWebCrawler() as crawler:
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# Stream results as they complete
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async for result in await crawler.arun_many(urls, config=run_conf):
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if result.success:
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print(f"[OK] {result.url}, length: {len(result.markdown.raw_markdown)}")
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else:
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print(f"[ERROR] {result.url} => {result.error_message}")
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# Or get all results at once (default behavior)
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run_conf = run_conf.clone(stream=False)
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results = await crawler.arun_many(urls, config=run_conf)
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for res in results:
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if res.success:
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print(f"[OK] {res.url}, length: {len(res.markdown.raw_markdown)}")
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else:
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print(f"[ERROR] {res.url} => {res.error_message}")
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if __name__ == "__main__":
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asyncio.run(quick_parallel_example())
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```
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The example above shows two ways to handle multiple URLs:
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1. **Streaming mode** (`stream=True`): Process results as they become available using `async for`
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2. **Batch mode** (`stream=False`): Wait for all results to complete
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For more advanced concurrency (e.g., a **semaphore-based** approach, **adaptive memory usage throttling**, or customized rate limiting), see [Advanced Multi-URL Crawling](../advanced/multi-url-crawling.md).
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---
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## 8. Dynamic Content Example
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Some sites require multiple “page clicks” or dynamic JavaScript updates. Below is an example showing how to **click** a “Next Page” button and wait for new commits to load on GitHub, using **`BrowserConfig`** and **`CrawlerRunConfig`**:
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```python
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import asyncio
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from crawl4ai import AsyncWebCrawler, BrowserConfig, CrawlerRunConfig, CacheMode
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from crawl4ai import JsonCssExtractionStrategy
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async def extract_structured_data_using_css_extractor():
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print("\n--- Using JsonCssExtractionStrategy for Fast Structured Output ---")
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schema = {
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"name": "KidoCode Courses",
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"baseSelector": "section.charge-methodology .w-tab-content > div",
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"fields": [
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{
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"name": "section_title",
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"selector": "h3.heading-50",
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"type": "text",
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},
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{
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"name": "section_description",
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"selector": ".charge-content",
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"type": "text",
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},
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{
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"name": "course_name",
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"selector": ".text-block-93",
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"type": "text",
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},
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{
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"name": "course_description",
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"selector": ".course-content-text",
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"type": "text",
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},
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{
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"name": "course_icon",
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"selector": ".image-92",
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"type": "attribute",
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"attribute": "src",
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},
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],
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}
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browser_config = BrowserConfig(headless=True, java_script_enabled=True)
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js_click_tabs = """
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(async () => {
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const tabs = document.querySelectorAll("section.charge-methodology .tabs-menu-3 > div");
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for(let tab of tabs) {
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tab.scrollIntoView();
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tab.click();
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await new Promise(r => setTimeout(r, 500));
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}
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})();
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"""
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crawler_config = CrawlerRunConfig(
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cache_mode=CacheMode.BYPASS,
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extraction_strategy=JsonCssExtractionStrategy(schema),
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js_code=[js_click_tabs],
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)
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async with AsyncWebCrawler(config=browser_config) as crawler:
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result = await crawler.arun(
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url="https://www.kidocode.com/degrees/technology", config=crawler_config
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)
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companies = json.loads(result.extracted_content)
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print(f"Successfully extracted {len(companies)} companies")
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print(json.dumps(companies[0], indent=2))
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async def main():
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await extract_structured_data_using_css_extractor()
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if __name__ == "__main__":
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asyncio.run(main())
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```
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**Key Points**:
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- **`BrowserConfig(headless=False)`**: We want to watch it click “Next Page.”
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- **`CrawlerRunConfig(...)`**: We specify the extraction strategy, pass `session_id` to reuse the same page.
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- **`js_code`** and **`wait_for`** are used for subsequent pages (`page > 0`) to click the “Next” button and wait for new commits to load.
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- **`js_only=True`** indicates we’re not re-navigating but continuing the existing session.
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- Finally, we call `kill_session()` to clean up the page and browser session.
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---
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## 9. Next Steps
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Congratulations! You have:
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1. Performed a basic crawl and printed Markdown.
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2. Used **content filters** with a markdown generator.
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3. Extracted JSON via **CSS** or **LLM** strategies.
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4. Handled **dynamic** pages with JavaScript triggers.
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If you’re ready for more, check out:
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- **Installation**: A deeper dive into advanced installs, Docker usage (experimental), or optional dependencies.
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- **Hooks & Auth**: Learn how to run custom JavaScript or handle logins with cookies, local storage, etc.
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- **Deployment**: Explore ephemeral testing in Docker or plan for the upcoming stable Docker release.
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- **Browser Management**: Delve into user simulation, stealth modes, and concurrency best practices.
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Crawl4AI is a powerful, flexible tool. Enjoy building out your scrapers, data pipelines, or AI-driven extraction flows. Happy crawling!
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