Scrapy obeys robots.txt rules by using a middleware called RobotsTxtMiddleware. This middleware is enabled by default when you create a new Scrapy project.
Here's how it works:
When Scrapy starts to crawl a website, it first fetches the robots.txt file from the root of the website. For example, if the website is http://example.com, Scrapy will fetch http://example.com/robots.txt.
Scrapy then parses the robots.txt file to find the rules that apply to it. The user agent for Scrapy is defined in the USER_AGENT setting in your project's settings file.
For each subsequent request, Scrapy checks whether the request is allowed by the robots.txt rules. If the request is not allowed, Scrapy will not continue to process the request.
If the ROBOTSTXT_OBEY setting is False, Scrapy will ignore the robots.txt rules and proceed with the request.
Remember, it's generally a good practice to respect robots.txt rules to avoid overloading servers or scraping data that the website owner has requested not to be scraped.