# Design a web crawler ## Reference * ## Usecases * Search engine * Copyright violation detection * keyword based finding * web walware detection * web analytics * datascience data ## Things to consider * Politeness/crawl rate * DNS query * Distributed crawling * Priority crawling * Duplicate detection ## Questions * How to generate content signature? * what to do with similar content? --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://liuzhenglaichn.gitbook.io/system-design/web-crawler/design-a-web-crawler.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.