Web scraping and crawling aren’t illegal by themselves unless people use them for harmful activities, such as competitive data mining, online fraud, account hijacking, data theft, stealing of intellectual property, or other illegal purposes.
The definition of web scraping is the act of automatically downloading a web page's data and extracting very specific information from it. The extracted information can be stored pretty much anywhere (database, file, etc.); web crawling is the act of automatically downloading a web page's data, extracting the hyperlinks it contains, and following them. The downloaded data is generally stored in an index or a database to make it easily searchable. While all the end results can be technically achieved by getting the data straight from any web browser, web scraping/crawling is more like a tool that eases the pain of collecting that data manually.
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