If a person makes changes to his website, how long would it take before Google notices them? It turns out that webmasters do not have to wait very long, but the duration would depend on a number of things. The scale of the Web makes it necessary for Google to prioritize certain pages over others.
The search giant used to crawl the Web every month but now it has the capacity to do this every few days. Spiders go out to look for new pages and revisit those, which are already on the index. If they find no changes in a site after a number of visits, then they may not go back to it as often. On the other hand, if the site has regular updates, then it may experience an increased their crawl rate.
The site’s ranking is also considered. Those that enjoy a high PageRank will be monitored quite closely. After all, a lot of people visit them and their content is deemed to have great importance. All of this happens automatically without the need to issue a request via Webmaster Tools.