Google uses a complex system of algorithms and computer programs, called "spiders" or "bots," to crawl the web and index new and updated content. The frequency at which a website is crawled can depend on several factors, such as how frequently the site is updated, its PageRank, and the number of links pointing to it.
For popular and frequently updated sites, Google may choose to crawl them in real-time or near-real-time to ensure that their search results are as up-to-date as possible. However, for other sites, the crawl frequency may be less frequent. The exact process of how Google determines its crawl schedule is not publicly disclosed, as it is a proprietary and constantly evolving part of their search algorithms.
Additionally, Google's real-time crawling capability is made possible by its ability to detect changes in websites quickly. Google's algorithms can identify when a webpage has been updated by monitoring signals such as changes in the HTML code, HTTP headers, or timestamps. This allows Google to prioritize the crawling of frequently updated pages and ensure that the most current information is available in search results.
Real-time crawling is especially important for websites that regularly publish news, blog posts, or other time-sensitive content. By crawling and indexing these sites in real-time, Google can provide users with the most recent and relevant information as quickly as possible.
It's worth noting that not all websites are crawled in real-time. The frequency at which a site is crawled depends on various factors, as mentioned earlier. Websites with lower traffic or less frequent updates may be crawled less often, resulting in a delay between making changes to the site and having those changes reflected in Google's search index.
Overall, real-time crawling is a result of Google's efforts to deliver the most accurate and up-to-date search results to its users by prioritizing the indexing of frequently updated websites.
In summary, Google crawls some websites in real-time to ensure that its search results are as current and accurate as possible. The frequency of real-time crawling is influenced by factors such as website updates, PageRank, and the number of links pointing to it. Google's algorithms can detect changes in websites quickly by monitoring various signals and prioritize crawling and indexing frequently updated pages. Real-time crawling is particularly important for news and time-sensitive content. However, not all websites are crawled in real-time, and the frequency of crawling can vary depending on various factors.